[{"id":"chicken","kind":"specimen","common":"Chicken","scientific":"Gallus gallus domesticus","group":"Birds","tags":["no-penis"],"measure":"No intromittent organ. Roosters have only a small non-intromittent phallus (two lateral lymphatic folds on the ventral lip of the vent); sperm is transferred by vent-to-vent contact","state":"none","valueMm":null,"confidence":"high","fact":"A chicken embryo starts to grow a phallus, but a Bmp4 signal makes its cells die off. Adult roosters mate by pressing their vent to the hen's.","marginNote":"Card intentionally left blank.","claims":[{"text":"Galliform cocks have only a non-intromittent phallus: two lymphatic folds on the ventral lip of the vent","source":1,"locator":"Galliformes chapter, 'Reproductive system'","quote":"The cock birds in all Galliformes have a non-intromittent phallus formed by two lateral folds (the lymphatic phallic bodies) situated on the ventral lip of the vent."},{"text":"Mating is by brief vent contact: the folds engorge with lymph and the everted vent is pressed to the hen's everted oviduct","source":1,"locator":"Galliformes chapter, 'Reproductive system'","quote":"During ejaculation, which is very rapid, the lymphatic bodies are momentarily engorged with lymph and the protruding vent is quickly applied to the protruding oviduct of the female. Semen is channelled between the two dilated lateral lymphatic phallic bodies."},{"text":"The chicken's copulatory apparatus is two papillae and a rudimentary copulatory organ in the vent","source":2,"locator":"'Male reproductive anatomy' section","quote":"The copulatory apparatus (phallus) of the chicken consists of two papillae and a rudimentary copulatory organ that is located in the vent (Scanes et al. 2004)."},{"text":"Chick embryos form a genital tubercle (the phallus precursor) that later regresses by apoptosis driven by Bmp4","source":3,"locator":"Abstract (Results)","quote":"Galliform embryos undergo cryptic development of a genital tubercle, the precursor of the phallus, but this later undergoes apoptosis, leading to regression of the tubercle. At the molecular level, a derived pattern of Bmp4 expression was identified in chick (a galliform) genital tubercles."},{"text":"Blocking Bmp signalling in chick genitalia prevents phallus regression; activating it in duck genitalia induces chicken-like cell death","source":3,"locator":"Abstract (Results)","quote":"Inhibition of Bmp signaling in chick genitalia rescues cells from apoptosis and prevents phallus regression, whereas activation of Bmp signaling in duck (an anseriform) genitalia induces a galliform-like pattern of apoptosis."},{"text":"Most Galliformes lack an intromittent phallus; waterfowl have well-developed ones","source":3,"locator":"Abstract (Results)","quote":"Galliformes (land fowl), most of which lack an intromittent phallus, and Anseriformes (waterfowl), which have well developed phalluses"},{"text":"Only about 3% of birds have retained a phallus capable of intromission","source":3,"locator":"Abstract (Background)","quote":"All birds reproduce by internal fertilization, but only ∼3% of birds have retained a phallus capable of intromission."},{"text":"In more than 97% of bird species, sperm is transferred by cloacal contact; some Galliformes have a pseudo-phallus","source":4,"locator":"§3.3 'Failure to obtain sperm'","quote":"In the majority of bird species (greater than 97%), sperm are obtained by the female through cloacal contact during copulation, although there are a few examples of extant bird species that copulate with the use of a true intromittent organ (e.g. in the ratites, many Tinamiformes, Anseriformes and Cracidae), or a pseudo-phallus (such as in some Galliformes) [ 125 – 127 ]."},{"text":"'3% of birds' traces to Briskie & Montgomerie 1997","source":5,"locator":"p.1, Introduction (reference 14 = Briskie & Montgomerie 1997, J Avian Biol 28:73–86)","quote":"Only 3% of all avian species possess a phallus, or intromittent organ [14], and these species are all members of basal lineages of extant birds [14,15]."}],"sources":[{"id":1,"label":"Coles B.H. (2009) Galliformes. In Tully T.N., Dorrestein G.M., Jones A.K. (eds) Handbook of Avian Medicine, 2nd edn. Saunders/Elsevier","doi":"10.1016/B978-0-7020-2874-8.00013-4","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC7149421/","type":"book","verified":"2026-10-30, full text via Europe PMC (Elsevier COVID-19 collection)"},{"id":2,"label":"Clark M.I. (2018) Management of breeding in small poultry production units. In Noakes D.E., Parkinson T.J., England G.C.W. (eds) Veterinary Reproduction and Obstetrics, 10th edn, ch. 30. Elsevier","doi":"10.1016/B978-0-7020-7233-8.00030-6","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC7149392/","type":"book","verified":"2026-10-30, full text via Europe PMC (Elsevier COVID-19 collection)"},{"id":3,"label":"Herrera A.M., Shuster S.G., Perriton C.L., Cohn M.J. (2013) Developmental basis of phallus reduction during bird evolution. Current Biology 23(12):1065–1074","doi":"10.1016/j.cub.2013.04.062","url":"https://doi.org/10.1016/j.cub.2013.04.062","type":"peer-reviewed","verified":"2026-10-30, abstract only (Europe PMC record). Publisher full text is free (bronze OA) but cell.com and sciencedirect.com returned 403 to all automated fetches"},{"id":4,"label":"Assersohn K., Brekke P., Hemmings N. (2021) Physiological factors influencing female fertility in birds. Royal Society Open Science 8:202274","doi":"10.1098/rsos.202274","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC8316823/","type":"peer-reviewed","verified":"2026-10-30, PMC full text"},{"id":5,"label":"Brennan P.L.R., Prum R.O., McCracken K.G., Sorenson M.D., Wilson R.E., Birkhead T.R. (2007) Coevolution of male and female genital morphology in waterfowl. PLoS ONE 2(5): e418","doi":"10.1371/journal.pone.0000418","url":"https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0000418","type":"peer-reviewed","verified":"2026-10-30, full text (PLoS PDF)"}],"imageRefs":[{"label":"Clark 2018, Veterinary Reproduction and Obstetrics, Fig. 30.7","what":"Diagram of a cockerel's reproductive tract ending in the cloaca (coprodeum, urodeum, proctodeum) and vent, with no external phallus"}],"artNotes":"With no intromittent organ to draw, the plate is an empty ruler. Anything showing the vent is schematic and not to scale, since we have no sourced dimensions for it. Clark Fig. 30.7 shows only internal anatomy.","artSimplifications":["No plate at true size (no intromittent organ)"],"plate":null,"portrait":{"src":{"256":"portraits/chicken/256.webp","640":"portraits/chicken/640.webp","1200":"portraits/chicken/1200.webp"},"w":1553,"h":1568,"alt":"A rooster, drawn side-on.","credit":"Drawn after a photo by Fir0002 (Wikimedia Commons, GFDL 1.2)."}},{"id":"flatworm","kind":"specimen","common":"Penis-fencing Flatworm","scientific":"Pseudoceros bifurcus","group":"Other invertebrates","tags":["microscopic"],"measure":"Penial stylet length as given in the species description ('Stylet short (130µm long)'); number of specimens not stated","state":"dissected","valueMm":0.13,"bodyMm":41.5,"bodyMeasure":"Body length of mature animals (midpoint of 23–60 mm; widths 10–35 mm), Heron Island, Great Barrier Reef","confidence":"low","fact":"These flatworms are hermaphrodites, and when two mate each tries to stab the other with its penis and inject sperm under the skin. Researchers call this 'penis fencing'.","claims":[{"text":"P. bifurcus is the species in which damaging 'penis fencing' sex was described","source":2,"locator":"Abstract (Nature 391:647)","quote":"One consequence seems to be that physically damaging sex, as occurs with the marine flatworm Pseudoceros bifurcus , might be favoured more in hermaphrodites than in species with separate sexes."},{"text":"During mating the worms evert their penis papillae and stylets and try to stab each other anywhere on the body, sometimes causing considerable damage","source":1,"locator":"p. 255 (Copulation)","quote":"During copulation animals were observed to move towards each other, touch, then roll around together, simultaneously everting their penis papillae and stylet(s) outward. They would then try to stab each other anywhere, sometimes causing considerable damage to their partner (Figs 44A, B; 48C, lower animal)."},{"text":"Sperm is injected under the skin and can be seen moving through the tissue","source":1,"locator":"p. 255 (Copulation)","quote":"During copulation, loose bundles of white spermatozoa were seen injected in the partner. The sperm could be observed as it moved into the parenchyma in white lines, presumably towards the oviducts."},{"text":"A successful stabber may hold on, stylet embedded, for up to five minutes","source":1,"locator":"p. 255 (Copulation)","quote":"When one animal was successful in penetrating the other, it often held on with its stylet embedded in the epidermis of its partner for up to five minutes"},{"text":"Wounds healed within 24 hours","source":1,"locator":"p. 255 (Copulation)","quote":"Animals with wounds were able to heal within 24 hours."},{"text":"Colour: blue to light mauve (cream in the largest animals), deepening to purple at the margin","source":1,"locator":"p. 216 (Colour & pattern)","quote":"Background varies from blue (279) to light mauve (250) (cream in the largest animals) intensifying to purple (252) at the margin; lacks distinct marginal band."}],"sources":[{"id":1,"label":"Newman L.J., Cannon L.R.G. (1994) Pseudoceros and Pseudobiceros (Platyhelminthes, Polycladida, Pseudocerotidae) from eastern Australia and Papua New Guinea. Memoirs of the Queensland Museum 37(1):205–266","url":"https://archive.org/details/biostor-105382","type":"peer-reviewed","verified":"2026-10-30, full text (BioStor PDF; OCR 'µm' glyphs corrected)"},{"id":2,"label":"Michiels N.K., Newman L.J. (1998) Sex and violence in hermaphrodites. Nature 391:647","doi":"10.1038/35527","type":"peer-reviewed","verified":"2026-10-30, abstract only (paywalled)"}],"imageRefs":[{"label":"Newman & Cannon 1994, Fig. 9 (p. 216)","what":"A: dorsal colour pattern; B: ventral wholemount (2.5 mm scale); C: reconstruction of the reproductive anatomy (500 µm scale)"},{"label":"Newman & Cannon 1994, Fig. 44 (p. 256)","what":"Copulatory behaviour sketches: A, Pseudoceros (two worms entwined); B, Pseudobiceros (both reared up with stylets extended)"},{"label":"Newman & Cannon 1994, Fig. 46A (colour plate, p. 258)","what":"Live P. bifurcus colour photograph"}],"artNotes":"At true size the stylet is a speck of 0.13 mm, so the plate adds a magnified inset. The source only calls the stylet 'short', so we drew a plain pointed spike.","artSimplifications":["Stylet shape not described in source; drawn as a simple pointed spike","Penis papilla omitted (length unknown)"],"plate":{"src":{"256":"plates/flatworm/256.webp","640":"plates/flatworm/640.webp","1600":"plates/flatworm/1600.webp","full":"plates/flatworm/full.webp"},"w":2308,"h":591,"pxPerMm":17041.5751,"a":[64.8,295.5],"b":[2280.4,295.5]},"portrait":{"src":{"256":"portraits/flatworm/256.webp","640":"portraits/flatworm/640.webp","1200":"portraits/flatworm/1200.webp"},"w":1422,"h":872,"alt":"A Pseudoceros flatworm, drawn from above with its white stripe.","credit":"Drawn after Newman and Cannon (1994), Fig. 46A."}},{"id":"bed-bug","kind":"specimen","common":"Bed bug","scientific":"Cimex lectularius","group":"Insects","tags":[],"measure":"Paramere (intromittent organ) length, approximate ('ca 500 µm'); rigid sclerotized structure, so state is immaterial; method and n not stated","state":"unknown","valueMm":0.5,"bodyMm":5.3,"bodyMeasure":"Male body length (Matsumura et al. citing Usinger 1966, Monograph of Cimicidae)","confidence":"medium","fact":"The male has a sickle-shaped spike, the paramere, about 0.5 mm long. He pierces the female's abdominal wall with it and inseminates straight into her body cavity; her genital tract is used only for laying eggs.","claims":[{"text":"Paramere is about 0.5 mm (500 µm) long","source":1,"locator":"Section 1 (Introduction)","quote":"the small size of its projectile, ca 500 µm in length"},{"text":"Traumatic insemination: the male pierces the female's abdominal wall with his genitalia and inseminates into her body cavity","source":2,"locator":"p.5683, Abstract","quote":"The bed bug, Cimex lectularius, has a unique mode of copulation termed ''traumatic'' insemination [Carayon, J. (1966) in Monograph of the Cimicidae, ed. Usinger, R. (Entomol. Soc. Am., Philadelphia), pp. 81–167] during which the male pierces the female's abdominal wall with his external genitalia and inseminates into her body cavity"},{"text":"The female genital tract is not used for copulation in any bed bug species; it is used only for egg laying","source":2,"locator":"p.5683, Introduction","quote":"The genital tract is not used for copulation in any members of the bed bug family (26) but functions solely in egg laying."},{"text":"Males always pierce at one site on the female's underside (the ectospermalege)","source":2,"locator":"p.5684, Fig. 1 caption","quote":"(B) The site of copulation on the ventrum of the female's abdomen. The male always copulates at this site (the ectospermalege)."},{"text":"Traumatic insemination reduces female longevity and reproductive success","source":2,"locator":"p.5683, Abstract","quote":"We show for the first time, to our knowledge, that traumatic insemination results in (i) last-male sperm precedence, (ii) suboptimal remating frequencies for the maintenance of female fertility, and (iii) reduced longevity and reproductive success in females."},{"text":"The paramere sits in a groove when not in use","source":2,"locator":"p.5684, Fig. 1 caption","quote":"(A) The intromittent organ of the male bed bug (a modified paramere). The groove in which the paramere sits when not in use is visible underneath the paramere. (Bar = 0.1 mm.)"},{"text":"The paramere is sickle-shaped, with short pegs on the upper side of its last third","source":1,"locator":"Section 3.3","quote":"The paramere is sickle-shaped (figure 5a,b) and covered with numerous short pegs on the dorsal side in the apical one-third (figure 5a–d)."},{"text":"The tip is the stiffest part and the base the most flexible; the paramere is slightly twisted and round in cross-section at the tip","source":1,"locator":"Abstract","quote":"Mechanical property gradients are present with the paramere tip as the stiffest region and the base as the most flexible one. … The paramere is slightly twisted; the tip region is circular in cross-section, and the geometry of the rest is rather complex."},{"text":"Male bed bugs are about 5.3 mm long","source":1,"locator":"Section 4.4","quote":"in comparison to 5.3 mm of male C. lectularius"}],"sources":[{"id":1,"label":"Matsumura Y., Krings W., Kovalev A., Gorb S.N. (2024) The puncture mechanics: an example from the bed bug Cimex lectularius showing traumatic insemination using the paramere. J. R. Soc. Interface 21:20240108","doi":"10.1098/rsif.2024.0108","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC11285789/","type":"peer-reviewed","verified":"2026-10-30, PMC full text read via WebFetch (sentences extracted on request, first ~100k of 129k characters); abstract read in full via NCBI E-utilities; Fig. 1, 5, 6 images downloaded from PMC CDN"},{"id":2,"label":"Stutt A.D., Siva-Jothy M.T. (2001) Traumatic insemination and sexual conflict in the bed bug Cimex lectularius. Proc. Natl. Acad. Sci. USA 98(10):5683–5687","doi":"10.1073/pnas.101440698","url":"https://www.pnas.org/doi/10.1073/pnas.101440698","type":"peer-reviewed","verified":"2026-10-30, full text read (PDF via Wayback Machine copy of pnas.org/content/98/10/5683.full.pdf)"}],"imageRefs":[{"label":"Matsumura et al. 2024, J R Soc Interface, Fig. 5a–b","what":"SEM of the isolated paramere, ventral (a) and dorsal (b) views, with 200 µm scale bars: sickle shape, taper, wing-shaped basal structure"},{"label":"Stutt & Siva-Jothy 2001, PNAS, Fig. 1A","what":"SEM of the paramere in situ on the male abdomen, lying in its groove, bar = 0.1 mm"},{"label":"Matsumura et al. 2024, J R Soc Interface, Fig. 1","what":"Habitus schematics of male and female with paramere and spermalege highlighted; mating snapshots"}],"artNotes":"Drawn from Matsumura Fig. 5a/b, which show the isolated organ from below and above, with Stutt Fig. 1A for how it curves in place. The true-size length is a straight line from the start of the free shaft to the tip, because that is what our two checks measured; the source's own value is approximate. The small wing-shaped flange is part of the same outline at the base. It is a single curve with no spiral.","artSimplifications":["Sensory pegs reduced to a few marks","Internal hollow/rolled structure not shown","Slight twist rendered as a gentle curve only"],"plate":{"src":{"256":"plates/bed-bug/256.webp","640":"plates/bed-bug/640.webp","1600":"plates/bed-bug/1600.webp","full":"plates/bed-bug/full.webp"},"w":2173,"h":659,"pxPerMm":4196.4048,"a":[52.6,128.2],"b":[2150.8,128.2]},"portrait":{"src":{"256":"portraits/bed-bug/256.webp","640":"portraits/bed-bug/640.webp","1200":"portraits/bed-bug/1200.webp"},"w":1331,"h":1038,"alt":"A male bed bug, drawn side-on.","credit":"Drawn after a CDC photo by Gary Alpert and Harold Harlan (Wikimedia Commons, public domain)."}},{"id":"seed-beetle","kind":"specimen","common":"Cowpea seed beetle","scientific":"Callosobruchus maculatus","group":"Insects","tags":["spines"],"measure":"Projected end-to-end length of the fully everted aedeagus with inflated endophallus (micro-CT rendering of one male frozen in copula), measured by us against the figure's 0.25 mm scale bar; includes parameres at the base","state":"everted","valueMm":0.86,"bodyMm":3.25,"bodyMeasure":"Adult body length, midpoint of the stated range 2.5–4 mm (sexes pooled; UF/IFAS extension text)","confidence":"low","fact":"The male's genitalia carry rigid spines that wound the female's copulatory duct during mating. Males with longer spines harm females more, and they also do better in sperm competition.","claims":[{"text":"Rigid genital spines cause internal injuries in females during copulation","source":2,"locator":"p.405, Figure 1 caption","quote":"The male genitalia of C. maculatus are armed with rigid spines that cause internal injuries in females during copulation."},{"text":"Longer spines correlate with more harm to females and with greater success in sperm competition","source":2,"locator":"p.404, Summary","quote":"We demonstrate that male spine length is positively correlated with harm to females during mating but also that males with longer spines are more successful in sperm competition."},{"text":"Injuries show up as melanized scars in the female copulatory duct","source":2,"locator":"p.405, Figure 1 caption","quote":"Males from populations with shorter genital spines leave females with less internal injuries ([C]; female mated once to a male from Oman) than do males from populations with longer spines ([D]; female mated once to a male from Volta). Arrows indicate melanized scars in the female copulatory duct."},{"text":"Spines pierce the female tract wall; wounding starts before the female begins kicking","source":1,"locator":"Abstract","quote":"In the seed beetle Callosobruchus maculatus, the male intromittent organ is covered in sharp spines that pierce the female copulatory tract wall during mating. … By scanning pairs flash-frozen at different times during mating, we show that significant tract wounding occurs before the onset of female kicking."},{"text":"The spines sit on an inflatable sac at the tip of the aedeagus and are exposed only when it inflates","source":4,"locator":"Materials and Methods","quote":"Male genital spines are located on the inflatable sac at the apex of the aedeagus and are exposed only upon inflation [19] ."},{"text":"Male elytron (wing-case) length is about 2.0 mm","source":5,"locator":"Discussion","quote":"male body size was about 0.8% smaller in the L lines compared to the S lines (mean elytra length; S: 2.04, s.e. = 0.011 mm, L: 2.03, s.e. = 0.007 mm)"}],"sources":[{"id":1,"label":"Dougherty L.R., Simmons L.W. (2017) X-ray micro-CT scanning reveals temporal separation of male harm and female kicking during traumatic mating in seed beetles. Proc. R. Soc. B 284:20170550","doi":"10.1098/rspb.2017.0550","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC5474075/","type":"peer-reviewed","verified":"2026-10-30, abstract read in full (Europe PMC); figure captions and methods checked via PMC page (WebFetch); Fig. 1 image downloaded. No text gives aedeagus dimensions"},{"id":2,"label":"Hotzy C., Arnqvist G. (2009) Sperm competition favors harmful males in seed beetles. Current Biology 19:404–407","doi":"10.1016/j.cub.2009.01.045","url":"https://www.cell.com/current-biology/fulltext/S0960-9822(09)00617-4","type":"peer-reviewed","verified":"2026-10-30, full text read (Cell open-archive PDF via Wayback Machine). Spine lengths are only plotted (Fig. 2 axis 38–54, units not legible in text extraction), not tabulated"},{"id":3,"label":"University of Florida / IFAS, Stored Product Pests Photographs CD-ROM: 'Cowpea weevil, Callosobruchus maculatus' (2005)","url":"https://entnemdept.ufl.edu/projex/gallery/dl/Stored_Product_Pests/text/cowpea_weevil.htm","type":"museum","verified":"2026-10-30, full page read"},{"id":4,"label":"van Lieshout E., McNamara K.B., Simmons L.W. (2014) Why do female Callosobruchus maculatus kick their mates? PLoS ONE 9(4):e95747","doi":"10.1371/journal.pone.0095747","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC3994112/","type":"peer-reviewed","verified":"2026-10-30, full text read (Europe PMC XML)"},{"id":5,"label":"Arnqvist G., Grieshop K., Hotzy C., Rönn J., Polak M., Rowe L. (2021) Direct and indirect effects of male genital elaboration in female seed beetles. Proc. R. Soc. B 288:20211068","doi":"10.1098/rspb.2021.1068","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC8261210/","type":"peer-reviewed","verified":"2026-10-30, full text read (Europe PMC XML)"}],"imageRefs":[{"label":"Dougherty & Simmons 2017, Proc R Soc B, Fig. 1c","what":"Micro-CT volume rendering of a fully everted aedeagus (lateral): parameres (P), end plate (EP), spiny region (AS), endophallus (E); 0.25 mm scale bar"},{"label":"Dougherty & Simmons 2017, Proc R Soc B, Fig. 1a–b","what":"Partly everted aedeagus: dense bottlebrush of long spines (lateral and end-on)"}],"artNotes":"Outline traced from Dougherty & Simmons 2017 Fig. 1c, a side view of the fully everted organ, with the look of the spines taken from Fig. 1a–b. The true-size length is a straight line from the base of the parameres to the far tip of the endophallus, matching our 0.86 mm measurement. It is drawn as one continuous outline, with the spines as attached triangles.","artSimplifications":["Spine count reduced (the real organ carries many tens of spines)","Internal structures and micro-CT colour omitted","Membranous wrinkles of the endophallus simplified"],"plate":{"src":{"256":"plates/seed-beetle/256.webp","640":"plates/seed-beetle/640.webp","1600":"plates/seed-beetle/1600.webp","full":"plates/seed-beetle/full.webp"},"w":2211,"h":960,"pxPerMm":2516.7705,"a":[30.3,484],"b":[2184.7,484]},"portrait":{"src":{"256":"portraits/seed-beetle/256.webp","640":"portraits/seed-beetle/640.webp","1200":"portraits/seed-beetle/1200.webp"},"w":1733,"h":970,"alt":"A male cowpea seed beetle, drawn side-on.","credit":"Drawn after a photo by limbatus (Wikimedia Commons, CC BY 2.0)."}},{"id":"burrowing-barnacle","kind":"specimen","common":"Burrowing barnacle (dwarf male)","scientific":"Cryptophialus minutus","group":"Crustaceans","tags":["relative-champion","microscopic"],"measure":"Length of the dissected penis 'when not stretched', from one dwarf male 0.30 mm long. Darwin's figure, converted to millimetres: 1.27 mm","state":"dissected","valueMm":1.27,"bodyMm":0.305,"bodyMeasure":"Greatest length of the same dwarf male the penis was dissected from (0.305 mm). Darwin gives mature males generally as about 0.33 mm, p. 585","confidence":"low","fact":"Darwin dissected a 1.27 mm penis out of a male barnacle only 0.30 mm long, about four times the male's length. He guessed it might extend to eight or nine times, and that guess is where the popular 'eight times its body length' barnacle figure comes from.","marginNote":"Darwin ended that sentence with an exclamation mark, which seems fair.","claims":[{"text":"Penis 1.27 mm unstretched, dissected from a male 0.30 mm long: about 4.2 times the male's length (measured)","source":1,"locator":"Vol. 2, p. 586","quote":"Out of a male, 12/1000ths of an inch in length, I dissected a penis, which, when not stretched, measured 50/1000ths of an inch in length;"},{"text":"DARWIN'S GUESS, not a measurement: a pulled portion stretched to 'apparently three times' its length, and Darwin thought the animal might extend the organ to 'perhaps' 2.54 mm, 'between eight and nine times' the male's length","source":1,"locator":"Vol. 2, p. 586","quote":"when a portion was pulled between two needles, it could be stretched to apparently three times its former length, and I should think that this organ could be extended by the animal to, perhaps, even the 100/1000ths of an inch,—that is, to between eight and nine times its own entire length!"},{"text":"The modern 'barnacle penises reach up to eight times body length' claim cites Darwin 1854, i.e. this guess for one dwarf male of Cryptophialus, not a measurement of an ordinary acorn barnacle","source":2,"locator":"Introduction, para. 1; Table 1","quote":"barnacles have evolved a remarkable mechanism for copulating with distant neighbours: penises that can extend up to eight times their body length ( Darwin 1854 ; table 1 )."},{"text":"The penis is immensely elongated, coiled up inside the male, articulated and muscular, and can presumably be protruded through a minute orifice","source":1,"locator":"Vol. 2, pp. 585–586","quote":"an immensely elongated probosciformed penis, coiled up and filling the rest of the inside of the sack down to the testis, which latter occupies the whole anterior, and generally lower end of the animal. This penis is plainly articulated, and includes fine transversely-striated muscles: no doubt it can be protruded through the minute orifice, and voluntarily moved about."},{"text":"The mature male is about 0.33 mm long, almost globular and slightly bilobed","source":1,"locator":"Vol. 2, p. 585","quote":"When the male is mature, its greatest length, measured from the posterior end, where the orifice is seated, to the anterior and blunter end, is about 13/1000ths of an inch, and therefore rather less than the pupa, which was 16/1000ths in length."},{"text":"Apart from testis, seminal vesicle and penis, the male has no mouth, thorax, cirri or other organs","source":1,"locator":"Vol. 2, p. 585","quote":"Internally there is no mouth, thorax, cirri, or other organs, excepting the testis and vesicula seminalis just mentioned, and an immensely elongated probosciformed penis"},{"text":"The whole male is scarcely larger than a single egg","source":1,"locator":"Vol. 2, p. 586","quote":"It should be borne in mind, that the whole male, including every part, is scarcely larger than a single ovum, of which sometimes sixty have to be impregnated by only two or three males."},{"text":"Usually four or five dwarf males live attached to one female (up to seven)","source":1,"locator":"Vol. 2, p. 584","quote":"I found from one or two up, in one case, to seven males, attached to the same female; four or five being the most usual number."},{"text":"Darwin called the female the smallest known cirripede; the largest he measured was under 2.5 mm","source":1,"locator":"Vol. 2, pp. 566–567","quote":"This, the smallest known cirripede, is flask-shaped and compressed … The largest specimen (fig. 2) which I have measured did not quite attain the length of one tenth of an inch."},{"text":"It lives burrowed, in vast numbers, in the shells of living Concholepas snails in the Chonos Archipelago, southern Chile","source":1,"locator":"Vol. 2, pp. 566–567","quote":"This cirripede inhabits, in vast numbers, the shells of the living Concholepas Peruviana, amongst the Chonos islands; the whole outside of the shell being sometimes completely drilled by its cavities"},{"text":"It was the first cirripede Darwin examined","source":1,"locator":"Vol. 2, p. 566, footnote","quote":"I am greatly indebted to Dr. Hooker, for having several years ago, when I examined this my first cirripede, aided me in many ways"}],"sources":[{"id":1,"label":"Darwin C. (1854) A Monograph on the Sub-class Cirripedia, with Figures of All the Species. The Balanidae (or Sessile Cirripedes); the Verrucidae, etc. London: Ray Society. pp. 566–586 (Cryptophialus minutus), Pl. 23–24","url":"https://archive.org/details/monographonsubcl02darw","type":"monograph","verified":"2026-10-30, full text: read on the page images of the archive.org/BHL scan (leaves n599–n601 = pp. 584–586, fractions checked on the image) and cross-checked against the Project Gutenberg transcription (ebook #46408)"},{"id":2,"label":"Neufeld C.J., Palmer A.R. (2008) Precisely proportioned: intertidal barnacles alter penis form to suit coastal wave action. Proceedings of the Royal Society B 275(1638):1081–1087","doi":"10.1098/rspb.2007.1760","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC2600913/","type":"peer-reviewed","verified":"2026-10-30, quote taken from the full-text PMC copy already read for the 'barnacle' dossier (content/barnacle/refs/neufeld2008_pmc.html)"}],"imageRefs":[{"label":"Darwin 1854, Pl. 24, fig. 19 (Cryptophialus minutus, mature male)","what":"The dwarf male: rounded, slightly bilobed sac, pointed upper lobe with the orifice (d), pupal antennae (a) at the attachment. Penis not shown (it is coiled inside)"},{"label":"Darwin 1854, Pl. 23, fig. 19 (Alcippe lampas, mature male, penis exserted)","what":"Closest figured relative: the dwarf male of Alcippe with its 'probosciformed penis, shown exserted' (m): a very long, thin, gently curved tube tapering to a fine tip. Darwin says the two males are 'truly surprising' in their resemblance"},{"label":"Darwin 1854, pp. 585–586 (page scans)","what":"The measurement text, for the verifier"}],"artNotes":"The penis is laid out in a gentle curve, with the tiny male at its base for scale; the true-size length is the penis alone (1.27 mm, dissected and unstretched). Darwin never figured the Cryptophialus penis, so we borrowed the outline and taper from his male of the related Alcippe lampas (Pl. 23 fig. 19), which he says is nearly identical apart from proportions. He calls it 'plainly articulated', so faint rings are drawn, but he gives no spacing and ours is schematic. His 2.54 mm 'extended' length was a guess and is left off the plate.","artSimplifications":["Penis outline borrowed from the related Alcippe lampas male (Darwin 1854, Pl. 23 fig. 19)","Articulations drawn schematically (spacing not given in the source)","Penis shown uncoiled; in life it is coiled inside the male","The male's antennae are omitted"],"plate":{"src":{"256":"plates/burrowing-barnacle/256.webp","640":"plates/burrowing-barnacle/640.webp","1600":"plates/burrowing-barnacle/1600.webp","full":"plates/burrowing-barnacle/full.webp"},"w":2384,"h":507,"pxPerMm":1514.8142,"a":[433.1,127.5],"b":[2353.6,127.5],"path":[[433.1,127.5],[464.9,131.1],[496.9,134.5],[528.7,137.5],[560.7,140],[592.6,142.4],[624.7,144.4],[656.7,145.9],[688.8,147.3],[720.8,148.3],[752.9,149.1],[785,149.5],[816.9,149.8],[849,149.7],[881.1,149.4],[913.2,149],[945.2,148.3],[977.3,147.4],[1009.4,146.3],[1041.3,145.1],[1073.4,143.6],[1105.4,142.1],[1137.4,140.4],[1169.5,138.6],[1201.4,136.8],[1233.4,134.8],[1265.5,132.7],[1297.5,130.6],[1329.4,128.5],[1361.4,126.4],[1393.5,124.3],[1425.5,122],[1457.4,119.9],[1489.4,117.8],[1521.5,115.8],[1553.4,113.9],[1585.4,111.9],[1617.5,110.2],[1649.5,108.5],[1681.6,107],[1713.5,105.6],[1745.6,104.3],[1777.6,103.3],[1809.7,102.4],[1841.8,101.7],[1873.8,101.2],[1905.9,101],[1938,101],[1969.9,101.2],[2002,101.8],[2034.1,102.5],[2066.1,103.6],[2098.2,105],[2130.2,106.6],[2162.3,108.7],[2194.2,110.9],[2226.2,113.6],[2258,116.5],[2290,119.9],[2321.8,123.6],[2353.6,127.5],[2353.6,127.5]]},"portrait":{"src":{"256":"portraits/burrowing-barnacle/256.webp","640":"portraits/burrowing-barnacle/640.webp","1200":"portraits/burrowing-barnacle/1200.webp"},"w":887,"h":1537,"alt":"A female burrowing barnacle, drawn as Darwin drew her.","credit":"Drawn after Darwin (1854), Plate 23, fig. 1."}},{"id":"guppy","kind":"specimen","common":"Guppy","scientific":"Poecilia reticulata","group":"Fish","tags":[],"measure":"Gonopodium length (modified anal fin), base of gonopodium to distal tip, excluding the hood; measured from photographs of the left side of live-collected adult males (least-squares mean adjusted for body length; SE 0.009 mm)","state":"unknown","valueMm":3.75,"bodyMm":16.5,"bodyMeasure":"Body length, snout to caudal peduncle, adult males from low-predation (LP) populations (same LP males as the headline)","confidence":"medium","fact":"The male guppy's 'penis' is a remodelled anal fin, the gonopodium. To mate, he moves it out of its resting position and inserts the tip into the female's genital pore.","marginNote":"Filed under fins, for administrative purposes.","claims":[{"text":"The male guppy's genital organ, the gonopodium, is a modified anal fin","source":1,"locator":"§1 Introduction, 'Trinidadian guppies' paragraph","quote":"Guppies are a promiscuous live‐bearing fish in which male genitalia are a modified anal fin known as the gonopodium (Houde, 1997 ; Magurran, 2005 )."},{"text":"In use, the gonopodium moves from rest to a copulatory position and its tip is inserted into the female genital pore","source":1,"locator":"§1 Introduction","quote":"Specifically, the gonopodium of Poecillid fishes is used to transfer sperm to the female during copulation (Houde, 1997 ; Magurran, 2005 ), in which case it moves from a resting position to a copulatory position so that the tip of the gonopodium is inserted in the female genital pore (Rosen & Tucker, 1961 )."},{"text":"Adult gonopodium about 3.7 mm (3.69 mm in high-predation, 3.75 mm in low-predation populations)","source":1,"locator":"§3 Results (Table 1; Fig. 2)","quote":"gonopodium length was—if anything—shorter (on average) in HP adult males than in LP adult males (HP males: 3.69 ± 0.012 mm, LP males: 3.75 ± 0.009 mm; Table 1 )."},{"text":"Adult males measure about 15–16.5 mm from snout to caudal peduncle","source":1,"locator":"§3 Results","quote":"both in adults (LP males: 16.5 ± 0.045, HP males: 14.98 ± 0.051 mm; ANCOVA: F 1,1,171 = 496.28, p < .001)"},{"text":"A male counts as mature when the hood (a sensory protuberance) extends beyond the gonopodium's tip (the hook)","source":1,"locator":"§2.2 Measurements and maturity status","quote":"Males were categorized as mature when the hood extended beyond the distal tip of the gonopodium (the hook), and immature when the hood was shorter than the gonopodium (Houde, 1997 )."},{"text":"Measurement method: gonopodium from base to distal tip, excluding the hood; body from snout to caudal peduncle","source":1,"locator":"§2.2 Measurements and maturity status","quote":"Body length (from snout to caudal peduncle) and gonopodium length (from base of gonopodium to distal tip, excluding the hood—see Kelly et al., 2000 ) were obtained from digital photographs using the software ImageJ"},{"text":"Juvenile males from high-predation streams had longer gonopodia than low-predation juveniles, but the difference vanished (or reversed) in adults","source":1,"locator":"§3 Results","quote":"By contrast, HP juveniles had (on average) longer gonopodia (standardized for body length) than LP juveniles (HP males: 3.67 ± 0.028 mm, LP males: 3.48 ± 0.025 mm; Table 1 )"}],"sources":[{"id":1,"label":"de Lira J.J.P.R., Yue Y., Levasseur S., Kelly C.D., Hendry A.P. (2021) The complex ecology of genitalia: Gonopodium length and allometry in the Trinidadian guppy. Ecology and Evolution 11(9):4564–4576","doi":"10.1002/ece3.7351","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC8093694/","type":"peer-reviewed","verified":"2026-10-30, full text (Europe PMC XML, CC BY)"}],"imageRefs":[{"label":"de Lira et al. 2021, Fig. 1 (adult)","what":"Lateral line drawing of an adult male guppy with the gonopodium hanging below the belly and the hood beside it; used for gonopodium length:width and placement on the body"}],"artNotes":"The plate shows the gonopodium alone, traced from de Lira et al. 2021 Fig. 1 and turned to lie horizontally; in life it hangs down at rest. The thin hood at the tip runs a little past the measured length. The reference figure shows no fin rays, so none are drawn.","artSimplifications":["Body drawn in outline only; colour pattern omitted","Fine structure of the gonopodium tip (hook/claw/serrae) not shown","Shown laid horizontally rather than hanging"],"plate":{"src":{"256":"plates/guppy/256.webp","640":"plates/guppy/640.webp","1600":"plates/guppy/1600.webp","full":"plates/guppy/full.webp"},"w":2424,"h":947,"pxPerMm":588.821,"a":[57.6,472.1],"b":[2265.7,472.1]},"portrait":{"src":{"256":"portraits/guppy/256.webp","640":"portraits/guppy/640.webp","1200":"portraits/guppy/1200.webp"},"w":1462,"h":728,"alt":"A male guppy, drawn side-on.","credit":"Drawn after a photo by Amy Deacon and colleagues (Wikimedia Commons, CC BY 4.0)."}},{"id":"garter-snake","kind":"specimen","common":"Red-sided Garter Snake","scientific":"Thamnophis sirtalis parietalis","group":"Reptiles","tags":["spines"],"measure":"Length of ONE manually everted hemipenis (the right one), from where it leaves the tail base to its free tip; measured by us against the millimetre ruler in the published photo (Friesen et al. 2014, Fig. 1). Only one hemipenis is used per mating; the plate shows the pair","state":"everted","valueMm":6.9,"bodyMm":472,"bodyMeasure":"Mean snout-vent length of adult males, red-sided garter snakes, Manitoba (same population as the hemipenis photo)","confidence":"low","fact":"A male garter snake has two hemipenes, each with a large spine at the base that works like a grappling hook during mating. The right one is larger, and males tend to alternate between them from one mating to the next.","marginNote":"Keeps a spare.","claims":[{"text":"Red-sided garter snake hemipenes are relatively simple cylinders with a ring of keratinized spines and a large, sharp basal spine","source":1,"locator":"§1 Introduction (Fig. 1)","quote":"sirtalis are relatively simple cylindrical structures [ 34 ], with a ring of keratinized spines and a large sharp basal spine located on the lateral aspect of the everted hemipenes that may also be associated with conflict over copulation duration ( figure 1 )."},{"text":"The basal spine is the largest spine and the first to contact the female; it has been likened to a grappling hook","source":1,"locator":"§1 Introduction","quote":"The basal spine is the largest hemipenial spine and the first to make contact with the female cloaca at intromission, and has been hypothesized to act as a grappling hook that allows the male to anchor and evert his hemipene into the female cloaca [ 37 ]."},{"text":"With the basal spine removed, copulations were shorter","source":1,"locator":"§4 Discussion, 'Spine-ablation'","quote":"As predicted, copulation duration decreased when the hemipenial basal spine was ablated."},{"text":"Right-side testes, kidneys and hemipenes are larger than the left","source":3,"locator":"Abstract","quote":"testes, kidneys, and hemipenes on the right-hand-side of the body are larger than those on the left."},{"text":"Males tend to alternate hemipenes in successive matings","source":3,"locator":"Abstract","quote":"Males tended to alternate hemipenis use in successive matings, perhaps because of depletion of plug material."},{"text":"At rest the hemipenes lie inside the tail, inside-out, with the spines facing inwards; eversion rotates the spines outward","source":4,"locator":"§1 Introduction","quote":"Hemipenes are kept inside the tail in an inverted position with the spines facing the inside of the hemipenis at rest. Eversion causes the spines to rotate around the everting edge of the hemipenis."},{"text":"Adult males average 47.2 cm snout to vent","source":2,"locator":"§2 Materials and methods, 'Animal housing and tissue collection'","quote":"All animals were adult snakes with a mean SVL of 47.2 cm (±0.67 SEM) for males and 54.6 cm (±0.96 SEM) for females"},{"text":"The common garter snake has simple subcylindrical hemipenes and shorter copulations than the plains garter snake, whose organs are bilobed","source":6,"locator":"Abstract","quote":"As predicted, copulation duration was significantly shorter in the common gartersnake (Thamnophis sirtalis), a species with simple subcylindrical hemipenes, than in the plains gartersnake (Thamnophis radix), a species with more complex, bilobed organs."},{"text":"Manual pressure often everts a snake hemipenis only partially","source":5,"locator":"p. 22, 'Everted'","quote":"Frequently, partial extrusion may be accomplished by manual pressure applied at the base of the ventral surface of the tail, a short distance posterior to the anal opening."}],"sources":[{"id":1,"label":"Friesen C.R., Uhrig E.J., Squire M.K., Mason R.T., Brennan P.L.R. (2014) Sexual conflict over mating in red-sided garter snakes (Thamnophis sirtalis) as indicated by experimental manipulation of genitalia. Proceedings of the Royal Society B 281(1774):20132694","doi":"10.1098/rspb.2013.2694","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC3843848/","type":"peer-reviewed","verified":"2026-10-30, full text (PMC HTML) and Fig. 1 image"},{"id":2,"label":"Lutterschmidt D.I., Lucas A.R., Karam R.A., Nguyen V.T., Rasmussen M.R. (2018) Sexually dimorphic patterns of cell proliferation in the brain are linked to seasonal life-history transitions in red-sided garter snakes. Frontiers in Neuroscience 12:364","doi":"10.3389/fnins.2018.00364","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC5992280/","type":"peer-reviewed","verified":"2026-10-30, full text (Europe PMC XML)"},{"id":3,"label":"Shine R., Olsson M.M., LeMaster M.P., Moore I.T., Mason R.T. (2000) Are snakes right-handed? Asymmetry in hemipenis size and usage in gartersnakes (Thamnophis sirtalis). Behavioral Ecology 11(4):411–415","doi":"10.1093/beheco/11.4.411","url":"https://academic.oup.com/beheco/article/11/4/411/178258","type":"peer-reviewed","verified":"2026-10-30, abstract only (full text paywalled)"},{"id":4,"label":"Keeffe R.M., Zhang B., Anderson P.S.L., Brennan P.L.R. (2025) Evolutionary morphology of genital spines informed by puncture mechanics. Proceedings of the Royal Society B 292(2053):20251698","doi":"10.1098/rspb.2025.1698","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC12364564/","type":"peer-reviewed","verified":"2026-10-30, full text (Europe PMC XML)"},{"id":5,"label":"Dowling H.G., Savage J.M. (1960) A guide to the snake hemipenis: a survey of basic structure and systematic characteristics. Zoologica 45(2):17–28","doi":"10.5962/p.203350","url":"https://www.biodiversitylibrary.org/part/203350","type":"peer-reviewed","verified":"2026-10-30, full text (BHL/BioStor PDF)"},{"id":6,"label":"King R.B., Jadin R.C., Grue M., Walley H.D. (2009) Behavioural correlates with hemipenis morphology in New World natricine snakes. Biological Journal of the Linnean Society 98(1):110–120","doi":"10.1111/j.1095-8312.2009.01270.x","type":"peer-reviewed","verified":"2026-10-30, abstract only (Europe PMC record)"}],"imageRefs":[{"label":"Friesen et al. 2014, Fig. 1","what":"Photo, lateral view, of both hemipenes everted side by side under the tail base with a cm ruler: short spiny cylinders, basal spine (arrow) on the right hemipenis. Used for length, width and shape"},{"label":"Dowling & Savage 1960, Text-fig. 5D","what":"Drawing of a spinose hemipenis with basal hooks in the congener Thamnophis radix (note: T. radix is bilobed, unlike T. sirtalis; use only for the look of the basal hooks)"}],"artNotes":"Both everted hemipenes are drawn, as in the photograph (Friesen 2014 Fig. 1), and the true-size length is that of one. The big basal hook follows a drawing of a related species, Thamnophis radix (Dowling & Savage 1960 Text-fig. 5D). Smaller spines are scattered as they appear in the photo. The tail is left off.","artSimplifications":["Individual small spines simplified to a stippled texture","Only a short section of tail drawn"],"plate":{"src":{"256":"plates/garter-snake/256.webp","640":"plates/garter-snake/640.webp","1600":"plates/garter-snake/1600.webp","full":"plates/garter-snake/full.webp"},"w":1095,"h":1370,"pxPerMm":137.6959,"a":[123.2,994.2],"b":[1073.4,994.2]},"portrait":{"src":{"256":"portraits/garter-snake/256.webp","640":"portraits/garter-snake/640.webp","1200":"portraits/garter-snake/1200.webp"},"w":2120,"h":701,"alt":"A red-sided garter snake, drawn in an S-curve.","credit":"Drawn after photos by Ethan Sahagun and J Hazard (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"domestic-cat","kind":"specimen","common":"Domestic Cat","scientific":"Felis catus","group":"Mammals","tags":["spines","baculum"],"measure":"Length of the free portion of the penis (state not stated; midpoint of 5–10 mm)","state":"unknown","valueMm":7.5,"rangeMm":[5,10],"bodyMm":551,"bodyMeasure":"Head-body length, mean of male stray and feral cats of all ages (n = 299), south-west Western Australia","confidence":"medium","fact":"A tomcat's penis carries 120 to 150 small spines pointing back towards the base. They depend on male hormones and regress within 5–6 weeks of neutering.","marginNote":"Individually modest.","claims":[{"text":"Spines 0.1–0.7 mm long, made of connective tissue under cornified epithelium, pointing away from the tip","source":1,"locator":"Section 'Penis'","quote":"The penile spines, which measure 0.1–0.7 mm in length, comprise connective tissue covered by cornified epithelium, which imparts rigidity. They point caudally, away from the tip of the penis, and lay flat against the penis unless it is erect."},{"text":"Spines cover about two-thirds of the penis from the base; the tip is smooth","source":1,"locator":"Section 'Penis'; Fig. 4","quote":"Once andro-gens are present in the postpubertal tom, penile spines become apparent on the glans penis, starting at the base and extending distally to cover approximately two-thirds of the penis ( Figure 4 ). The tip of the penis is free of spines and has a smooth appearance."},{"text":"Spines regress within 5–6 weeks of castration","source":1,"locator":"Section 'Penis'","quote":"The spines are dependent on androgens; therefore, once the tom is castrated, they will regress within 5–6 weeks."},{"text":"Some toms have a 3–5 mm os penis (baculum)","source":1,"locator":"Section 'Penis'","quote":"Some tom cats will have an os penis, a small bone (3–5 mm) within the glans portion of the penis."},{"text":"120 to 150 spines on the glans of a mature tom","source":3,"locator":"Chapter 'Male Reproduction' (as reproduced on veteriankey.com)","quote":"The glans of the penis of a mature tom cat is covered with 120 to 150 penile spines that are directed caudally."},{"text":"The penis points backwards unless erect","source":1,"locator":"Section 'Penis'","quote":"The penis is located ventrally to the testicles and points caudally unless erect ( Figure 2 )."}],"sources":[{"id":1,"label":"Johnson A.K. (2022) Normal feline reproduction: The tom. Journal of Feline Medicine and Surgery 24(3):212–220","doi":"10.1177/1098612X221079707","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC10845405/","type":"peer-reviewed","verified":"2026-10-30, PMC full text (HTML) read"},{"id":2,"label":"Fleming P.A., Crawford H.M., Auckland C.H., Calver M.C. (2020) Body size and bite force of stray and feral cats—are bigger or older cats taking the largest or more difficult-to-handle prey? Animals 10(4):707","doi":"10.3390/ani10040707","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC7222765/","type":"peer-reviewed","verified":"2026-10-30, PMC full text (HTML) read; Table 1a columns are Males then Females"},{"id":3,"label":"Little S.E. (ed.) The Cat: Clinical Medicine and Management, Chapter 39 'Male Reproduction' (read as a search excerpt)","url":"https://veteriankey.com/male-reproduction/","type":"book","verified":"2026-10-30, quote seen only as a search-engine excerpt; page not opened and textbook not identified"}],"imageRefs":[{"label":"Johnson 2022, Fig. 4","what":"Photo of the extruded penis of an intact tom: smooth preputial fold at base, conical glans with caudally pointing spines, smooth tip. No scale bar."}],"artNotes":"Only the free part is drawn, from the preputial fold to the tip (7.5 mm); no source we could read gives the length of the part inside the prepuce. The 120–150 spine count comes from a secondary textbook excerpt, so the spines are a field of small marks rather than an exact tally. They are drawn raised, as in erection; otherwise they lie flat. The preputial fold at the base is drawn in simplified form from Johnson 2022 Fig. 4; the true-size length covers only the free part in front of it.","artSimplifications":["Spines drawn as a stylised field of small marks; count not exact","Os penis not shown (present only in some toms)","Colour from a single photograph"],"plate":{"src":{"256":"plates/domestic-cat/256.webp","640":"plates/domestic-cat/640.webp","1600":"plates/domestic-cat/1600.webp","full":"plates/domestic-cat/full.webp"},"w":2100,"h":1317,"pxPerMm":202.2848,"a":[558,659],"b":[2075.1,659]},"portrait":{"src":{"256":"portraits/domestic-cat/256.webp","640":"portraits/domestic-cat/640.webp","1200":"portraits/domestic-cat/1200.webp"},"w":2309,"h":1441,"alt":"A black-and-white tomcat, drawn side-on.","credit":"Drawn after a photo by Szczecinolog (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"spider","kind":"specimen","common":"Spider (male palp): electric-blue tarantula","scientific":"Chilobrachys natanicharum","group":"Arachnids","tags":[],"measure":"Palpal bulb + embolus length (PBL + ELS: start of subtegulum to end of tegulum, plus embolus along a straight line with the bulb); the sperm-transfer part of the male pedipalp, not a penis; holotype male","state":"unknown","valueMm":8.02,"rangeMm":[4.03,8.02],"bodyMm":38.51,"bodyMeasure":"Total length including chelicerae, same holotype male","confidence":"low","fact":"Male spiders have no penis. The male ejaculates onto a small sperm web, sucks the sperm up into a bulb at the tip of each pedipalp, and delivers it through a knife-like embolus. In this tarantula's holotype, bulb plus embolus measures 8.02 mm.","marginNote":"The palp works much like a laboratory pipette, filled at the sperm web and emptied into the female.","claims":[{"text":"Bulb + embolus of the holotype male is 8.02 mm; bulb 2.59 mm long, 4.28 mm wide; embolus 5.43 mm (straight), 7.10 mm along the curve","source":1,"locator":"Description, Holotype ♂","quote":"Palp bulb and embolus (PBL+ELS) 8.02 long, dark reddish brown, palp bulb spherical and partly concave; palp bulb width (PBW) 4.28 and length (PBL) 2.59; embolus width (EW) 3.65 and length along a straight line with the bulb (ELS) 5.43; embolus length along the curve (ELC) 7.10 (Fig. 7A–E )."},{"text":"The second male measured (paratype) had a bulb + embolus of only 4.03 mm despite a larger body (55.75 mm)","source":1,"locator":"Description, Paratype ♂ ELB02","quote":"Paratype ♂ ELB02: total length 55.75 (including chelicerae) … Palp bulb and embolus (PBL+ELS) 4.03 long, dark reddish brown, palp bulb spherical and partly concave, width (PBW) 2.56, length (PBL) 1.36"},{"text":"The whole holotype pedipalp (femur to tarsus) is 33.05 mm long","source":1,"locator":"Table 1 (holotype ♂ leg and palp measurements, mm)","quote":"Table 1. Legs and palp measurements (in mm) of holotype ♂ THNHM-At-00000062 … Total 66.71 55.91 50.10 64.29 33.05"},{"text":"The embolus is flat and knife-like, wide at the base; the bulb is twisted by 40°","source":1,"locator":"Description, Holotype ♂","quote":"Embolus wide at base and flat, knife-like in shape. … Palp bulb twisted at 40° angle between lowest and highest points of embolus (ALH) (Fig. 14A, B )."},{"text":"In spiders the male's pedipalps, not a penis, are the copulatory organs","source":2,"locator":"Section on spider body plan (Introduction)","quote":"The pedipalps of adult males are modified into copulatory organs and facilitate the transfer of sperm to mature females."},{"text":"Males first ejaculate onto a sperm web, then suck the sperm up into their palps (sperm induction)","source":3,"locator":"Discussion","quote":"It is plausible that during sperm induction—a process unique to spiders during which a male ejaculates from gonopore onto sperm web and then sucks the sperm into his palps—the male will intentionally charge one palp more than the other."},{"text":"The embolus is the part that actually goes into the female","source":4,"locator":"Results","quote":"The embolus is the actual intromitting organ; it intakes sperm during sperm induction and releases it into the female epigyne."},{"text":"Holotype male body length 38.51 mm","source":1,"locator":"Description, Holotype ♂","quote":"total length 38.51 (including chelicerae)"}],"sources":[{"id":1,"label":"Chomphuphuang N., Sippawat Z., Sriranan P., Piyatrakulchai P., Songsangchote C. (2023) A new electric-blue tarantula species of the genus Chilobrachys Karsch, 1892 from Thailand (Araneae, Mygalomorphae, Theraphosidae). ZooKeys 1180:105–128","doi":"10.3897/zookeys.1180.106278","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC10520723/","type":"peer-reviewed","verified":"2026-10-30, full text read (Europe PMC XML, open access CC BY); Figs 1, 3, 7 downloaded from PMC"},{"id":2,"label":"Mammola S., Michalik P., Hebets E.A., Isaia M. (2017) Record breaking achievements by spiders and the scientists who study them. PeerJ 5:e3972","doi":"10.7717/peerj.3972","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC5668680/","type":"peer-reviewed","verified":"2026-10-30, full text read (Europe PMC XML)"},{"id":3,"label":"Zhang S., Yu L., Tan M., Tan N.Y.L., Wong X.X.B., Kuntner M., Li D. (2022) Male mating strategies to counter sexual conflict in spiders. Communications Biology 5:534","doi":"10.1038/s42003-022-03512-8","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC9163124/","type":"peer-reviewed","verified":"2026-10-30, full text read (Europe PMC XML)"},{"id":4,"label":"Sentenská L., Müller C.H.G., Pekár S., Uhl G. (2017) Neurons and a sensory organ in the pedipalps of male spiders reveal that it is not a numb structure. Scientific Reports 7:12209","doi":"10.1038/s41598-017-12555-5","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC5610179/","type":"peer-reviewed","verified":"2026-10-30, full text read (Europe PMC XML)"}],"imageRefs":[{"label":"Chomphuphuang et al. 2023, ZooKeys 1180, Fig. 7A–D","what":"Holotype male palpal bulb in prolateral, retrolateral, dorsal and ventral views (scale bars 1 mm): spherical dark red-brown bulb with long flat knife-like embolus"},{"label":"Chomphuphuang et al. 2023, ZooKeys 1180, Fig. 3","what":"Bulb outline with the measured dimensions (PBL, ELS, PBW, EW, ELC) marked: defines the scaling anchor"},{"label":"Chomphuphuang et al. 2023, ZooKeys 1180, Fig. 1B","what":"Live holotype male (for the mascot; violet-blue legs)"}],"artNotes":"Traced from Fig. 7B (retrolateral view) and the outline in Fig. 3. The true-size length is a straight line along the bulb's axis from the start of the subtegulum to the embolus tip, which is how the paper defines its 8.02 mm bulb-plus-embolus length. Bulb and embolus share one outline. What is drawn is the sperm-transfer bulb at the tip of the male's pedipalp; spiders have no penis. The scale bar in Fig. 7E disagrees with panels A–D, so we followed A–D. We also shortened the outline by about 10% so it matches the paper's stated measurements (8.02 mm bulb plus embolus, bulb 4.28 mm wide), which differ slightly from the photograph.","artSimplifications":["Embolus keels and fine sclerite boundaries omitted","Rest of the pedipalp (cymbium and leg-like segments) not drawn","40° twist shown only as a gentle curve"],"plate":{"src":{"256":"plates/spider/256.webp","640":"plates/spider/640.webp","1600":"plates/spider/1600.webp","full":"plates/spider/full.webp"},"w":2178,"h":1212,"pxPerMm":210.0895,"a":[470.5,627.2],"b":[2155.4,627.2]},"portrait":{"src":{"256":"portraits/spider/256.webp","640":"portraits/spider/640.webp","1200":"portraits/spider/1200.webp"},"w":1674,"h":1196,"alt":"A male electric-blue tarantula, drawn side-on.","credit":"Drawn after Chomphuphuang et al. (2023), Fig. 1B (CC BY 4.0)."}},{"id":"barnacle","kind":"specimen","common":"Acorn Barnacle","scientific":"Balanus glandula","group":"Crustaceans","tags":["relative-champion"],"measure":"Relaxed (not inflated) penis length of thawed, extracted soma; the 'standard length' to which the field-survey analyses were standardised (Barkley Sound, BC)","state":"dissected","valueMm":9.21,"bodyMm":8,"bodyMeasure":"Shell basal width (diameter) of the 'standard-sized' barnacle used in the same survey (soma wet mass 0.0172 g); acorn barnacles are measured across the base, not head to tail","confidence":"medium","fact":"On wave-battered shores these barnacles have shorter, stouter penises than in sheltered bays, and barnacles transplanted from one to the other grew penises to suit their new shore.","marginNote":"On these shores the weather does the tailoring, cutting them shorter and stouter wherever the waves are rough.","claims":[{"text":"Penises on wave-exposed shores are shorter and stouter than in protected bays, and more than twice as massive for their length","source":1,"locator":"Abstract","quote":"We observed that penises of an intertidal barnacle ( Balanus glandula ) from wave-exposed shores were shorter than, stouter than, and more than twice as massive for their length as, those from nearby protected bays."},{"text":"Barnacles transplanted to an exposed coast grew shorter, wider penises than those moved to a sheltered harbour (phenotypic plasticity)","source":1,"locator":"Abstract","quote":"Finally, field experiments confirmed that most of this variation was due to phenotypic plasticity: barnacles transplanted to a wave-exposed outer coast produced dramatically shorter and wider penises than counterparts moved to a protected harbour."},{"text":"After 20 weeks, transplants to the exposed shore had penises 25% shorter and 20% wider than those moved to the harbour","source":1,"locator":"Results §3(c)","quote":"When corrected for body size, barnacles transplanted to the wave-exposed shore produced 25% shorter (analysis of covariance on log-transformed data, F 1,45 =15.46, p <0.001; figure 4 a ) and 20% wider ( F 1,46 =11.57, p =0.001; figure 4 b ) penises than counterparts moved to the protected harbour after a period of 20 weeks."},{"text":"Fully inflated penises were on average about 1.75–1.82 times their relaxed length","source":1,"locator":"Figure 1 caption","quote":"(mean proportional inflation±s.e.m.: protected shore=1.82±0.082; exposed shore=1.75±0.044; p =0.77)"},{"text":"Barnacle penises are said to reach up to eight times body length; the reference given is Darwin 1854","source":1,"locator":"Introduction §1; Table 1","quote":"barnacles have evolved a remarkable mechanism for copulating with distant neighbours: penises that can extend up to eight times their body length ( Darwin 1854 ; table 1 )."},{"text":"Origin of the 'eight times' figure: Darwin's estimate for one dwarf male of a different species, the burrowing barnacle Cryptophialus minutus. The male was about 0.30 mm long, its unstretched penis about 1.27 mm, and Darwin guessed it might extend to about 2.54 mm","source":3,"locator":"pp. 585–586 (Cryptophialus minutus, Male)","quote":"Out of a male, 12/1000ths of an inch in length, I dissected a penis, which, when not stretched, measured 50/1000ths of an inch in length; when a portion was pulled between two needles, it could be stretched to apparently three times its former length, and I should think that this organ could be extended by the animal to, perhaps, even the 100/1000ths of an inch,—that is, to between eight and nine times its own entire length!"},{"text":"In the source table, B. glandula's extended penis is 3.6 times body length (unpublished data)","source":1,"locator":"Table 1","quote":"Pacific acorn barnacle Balanus glandula 3.6 C. J. Neufeld (unpublished data)"}],"sources":[{"id":1,"label":"Neufeld C.J., Palmer A.R. (2008) Precisely proportioned: intertidal barnacles alter penis form to suit coastal wave action. Proceedings of the Royal Society B 275(1638):1081–1087","doi":"10.1098/rspb.2007.1760","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC2600913/","type":"peer-reviewed","verified":"2026-10-30, full text (PMC HTML) and figures"},{"id":2,"label":"Neufeld C.J. (2011) Morphological plasticity of barnacle feeding legs and penises. PhD thesis, University of Alberta (Chapter 2 = Neufeld & Palmer 2008)","url":"https://era.library.ualberta.ca/items/80045f94-9ef8-4582-8377-be4223551456","type":"other","verified":"2026-10-30, full PDF (p. 33 rendered)"},{"id":3,"label":"Darwin C. (1854) A Monograph on the Sub-class Cirripedia. Vol. 2: The Balanidae, the Verrucidae, etc. London: Ray Society","url":"https://darwin-online.org.uk/content/frameset?itemID=F339.2&viewtype=text&pageseq=1","type":"monograph","verified":"2026-10-30, full text (darwin-online transcription)"}],"imageRefs":[{"label":"Neufeld 2011 thesis Fig. 2-4b (= Neufeld & Palmer 2008 Fig. 3b)","what":"Lateral photo of a relaxed, extracted penis (exposed-shore animal, basal width 8.9 mm), 2 mm scale bar: tapering, gently S-curved tube"},{"label":"Neufeld & Palmer 2008 Fig. 3a","what":"Protected-shore penis: longer and more slender, same view"}],"artNotes":"Drawn relaxed, as in the photograph (Fig. 2-4b): a single smooth, tapering tube with a soft S-curve. The 9.21 mm runs along the centreline from base to tip. Because the penis curves and sits a little out of plane, proportions measured off the photo are only good to about ±10%. The colour is unknown; the text does not mention it and the photographs are greyscale.","artSimplifications":["Cuticle annulations simplified to faint rings","Shell and feeding legs (cirri) omitted","Colour not sourced (greyscale photos only)"],"plate":{"src":{"256":"plates/barnacle/256.webp","640":"plates/barnacle/640.webp","1600":"plates/barnacle/1600.webp","full":"plates/barnacle/full.webp"},"w":2082,"h":334,"pxPerMm":223.1317,"a":[39.9,252.9],"b":[2042.7,252.9],"path":[[39.9,252.9],[50.4,251],[65.5,248.6],[82.8,245],[100.4,239.9],[118,232.7],[136.7,223.7],[155.8,214],[174.7,204.3],[192.9,194.6],[211.1,184.6],[229.2,174.4],[247.5,164.7],[265.8,155.1],[284.1,145.4],[302.7,136.6],[321.8,129.1],[341.5,123.6],[361.7,119.4],[382.3,116.1],[402.8,113.1],[423.6,110.9],[444.7,109.1],[465.7,107.6],[486.5,105.1],[507.1,101.7],[527.2,97.4],[547.3,93.1],[567.7,89.3],[588,85.6],[608.4,82],[628.9,79],[650,77.3],[671.7,77.1],[693.7,78.4],[715.9,80],[737.8,81],[759.6,81.3],[781.3,81.3],[802.8,81.1],[824.3,80.9],[845.8,80.3],[867,79.3],[888.5,78.7],[910.1,78.7],[932,79.9],[954.4,81.6],[976.7,83.9],[999.3,86.4],[1021.9,89.4],[1044.7,92.7],[1067.6,96.3],[1090.5,100.1],[1113.5,104.1],[1136.7,108.6],[1159.9,113.1],[1183,117.7],[1206.1,121.7],[1229.1,125.7],[1252.2,130],[1275.6,135.3],[1299.5,141.7],[1323.6,149.1],[1347.9,157],[1372.2,164.6],[1396.4,171.9],[1420.4,179],[1444.5,186.3],[1468.8,194],[1493.4,202.3],[1518,211.1],[1542.5,219.7],[1566.8,227.3],[1590.7,233.9],[1614.3,239.6],[1637.7,244.7],[1660.8,248.9],[1683.4,251.9],[1705.9,254.1],[1727.9,255.6],[1749.9,256.6],[1771.6,256.6],[1793,256],[1814.2,255],[1835.7,254.4],[1857.2,254.1],[1878.8,254.1],[1900.5,254.1],[1922.1,254.1],[1945,254.1],[1968.6,254.1],[1990.7,254.1],[2008.7,254],[2021.7,253.7],[2031.2,253.4],[2037.9,253],[2042.7,252.9],[2042.7,252.9]]},"portrait":{"src":{"256":"portraits/barnacle/256.webp","640":"portraits/barnacle/640.webp","1200":"portraits/barnacle/1200.webp"},"w":1334,"h":1088,"alt":"An acorn barnacle, drawn side-on with its feeding legs out.","credit":"Drawn after a photo by WindBorneListener (Wikimedia Commons, CC0)."}},{"id":"serotine-bat","kind":"specimen","common":"Serotine Bat","scientific":"Eptesicus serotinus","group":"Mammals","tags":[],"measure":"Length of the erect penis shaft (Fig. 1C, scale line [1]); from the figure it appears to run from the base to the tip of the terminal swelling","state":"erect","valueMm":16.4,"bodyMm":72,"bodyMeasure":"Head-body length, midpoint of the species range 62–82 mm (not the same animals)","confidence":"medium","fact":"Erect, the serotine bat's penis is about seven times longer than the female's vagina, and it never goes in. The male presses its heart-shaped tip against her vulva instead.","marginNote":"The authors call it a 'copulatory arm', which makes the whole business sound like a rather formal handshake.","claims":[{"text":"The penis is used as a 'copulatory arm' rather than an intromittent organ","source":1,"locator":"Summary, p. R1182","quote":"Here, we show that in serotine bats ( Eptesicus serotinus ) the penis is used as a ‘copulatory arm’ rather than an intromittent organ, revealing a novel copulatory behaviour in mammals."},{"text":"The terminal swelling is pressed against the vulva without vaginal intromission","source":1,"locator":"Fig. 1D caption, p. R1182","quote":"The terminal swelling of the erect penis is firmly pressed against the vulva, without vaginal intromission."},{"text":"Terminal swelling 7.5 mm wide; vagina outer diameter 1.1 mm; cervix 0.7 mm","source":1,"locator":"Fig. 1 caption, p. R1182","quote":"[2] Width of the erect penis terminal swelling (7.5 mm). [3] Outer diameter of the cervix (0.7 mm) and [4] vagina (1.1 mm)."},{"text":"Erect penis about seven times longer and wider than the vagina, and about a fifth of head-body length","source":2,"locator":"Cell Press news release (EurekAlert! 1008279), 20 Nov 2023","quote":"Their measurements showed that, when erect, serotine bat penises are around seven times longer and seven times wider than serotine bat vaginas, and about a fifth as long as the bats' head-body length."},{"text":"Heart-shaped head","source":2,"locator":"Cell Press news release (EurekAlert! 1008279), 20 Nov 2023, opening paragraph","quote":"The bats' penises are around seven times longer than their partners' vaginas and have a \"heart-shaped\" head"},{"text":"97 mating events analysed; half of the recorded copulations lasted less than 53 minutes, the longest 12.7 hours","source":2,"locator":"Cell Press news release (EurekAlert! 1008279), 20 Nov 2023","quote":"Altogether, the team analyzed 97 mating events—93 from the Dutch church and 4 from the Ukrainian bat rehabilitation center. On average, these interactions lasted less than 53 minutes, but the longest event extended to 12.7 hours."}],"sources":[{"id":1,"label":"Fasel N.J., Jeucken J., Kravchenko K., Fritze M., Ruczyński I., Komar E., Moiseienko M., Shulenko A., Vlaschenko A., Christe P., Glaizot O., Holtze S. (2023) Mating without intromission in a bat. Current Biology 33(22):R1182–R1183","doi":"10.1016/j.cub.2023.09.054","url":"https://www.cell.com/current-biology/fulltext/S0960-9822(23)01304-0","type":"peer-reviewed","verified":"2026-10-30: Summary, Figure 1 image and full Figure 1 caption read from a verbatim CC BY 4.0 reproduction credited to the paper (rosarubicondior.blogspot.com, Nov 2023). Main text and supplement NOT read: cell.com and sciencedirect return 403 to automated access. The paper is open access (Unpaywall, publisher OA)."},{"id":2,"label":"Cell Press (2023) Serotine bats mate without penetration [news release on the Fasel et al. 2023 paper], EurekAlert!, 20 Nov 2023","url":"https://www.eurekalert.org/news-releases/1008279","type":"news","verified":"2026-10-30, full release read (WebFetch)"},{"id":3,"label":"Wilson D.E., Mittermeier R.A. (eds) (2019) Handbook of the Mammals of the World, Vol. 9: Bats. Lynx Edicions, Barcelona. Vespertilionidae, Eptesicus serotinus account, pp. 850–851","doi":"10.5281/zenodo.6568073","url":"https://treatment.plazi.org/id/4C3D87E8-FFA7-6A19-FA55-92441429BF30","type":"monograph","verified":"2026-10-30, Plazi TreatmentBank full treatment text"}],"imageRefs":[{"label":"Fasel et al. 2023, Fig. 1A,B","what":"Erect penis, ventral (A) and dorsal (B) views, painted illustrations with 1 cm scale bars: slender shaft, heart-shaped two-lobed terminal swelling"},{"label":"Fasel et al. 2023, Fig. 1 (full) and 1D","what":"Full figure incl. scale lines [1] 16.4 mm and [2] 7.5 mm overlaid on the female tract (C) and the copulation posture (D)"}],"artNotes":"The true-size length runs from the base of the shaft to the far tip of the heart-shaped swelling (16.4 mm), since scale line [1] in Fig. 1C seems to cover the whole erect organ; the caption does not say exactly where the shaft begins. The view is from below (ventral), as in Fasel et al. 2023 Fig. 1A, the only reference showing the full length. Colours are from the painted figure.","artSimplifications":["Hair on and around the swelling omitted","Surface vessels omitted","Colours taken from the published painting"],"plate":{"src":{"256":"plates/serotine-bat/256.webp","640":"plates/serotine-bat/640.webp","1600":"plates/serotine-bat/1600.webp","full":"plates/serotine-bat/full.webp"},"w":2384,"h":1114,"pxPerMm":140.8413,"a":[45.3,559.5],"b":[2355.2,559.5]},"portrait":{"src":{"256":"portraits/serotine-bat/256.webp","640":"portraits/serotine-bat/640.webp","1200":"portraits/serotine-bat/1200.webp"},"w":1633,"h":1175,"alt":"A serotine bat in flight, drawn side-on.","credit":"Drawn after a photo by Mnolf (Wikimedia Commons, CC BY-SA 3.0)."}},{"id":"euro-coin","kind":"reference-object","common":"€1 coin","scientific":"","group":"Reference objects","tags":[],"measure":"Coin diameter (€1, round)","state":"unknown","valueMm":23.25,"confidence":"high","fact":"EU law sets the €1 coin at 23.25 mm across, 2.33 mm thick and 7.5 g. The outer ring is yellow nickel-brass and the white centre has three layers.","marginNote":"Its diameter is fixed in EU law, so this is about as round as legislation can make a thing.","claims":[{"text":"Diameter 23.25 mm, thickness 2.33 mm, weight 7.5 g (columns: diameter mm, thickness mm, weight g)","source":1,"locator":"Annex I, header and row '1'","quote":"Face value (euro) Diameter in mm Thickness in mm Weight in gr Shape Colour Composition Edge … 1 23,25 2,33 7,5 Round"},{"text":"Outer ring yellow nickel-brass; inner part white, three layers; interrupted milled edge","source":1,"locator":"Annex I, row '1'","quote":"External part: yellow Nickel-brass (CuZn20Ni5) Interrupted milled Internal part: white Three-layers: Cu75Ni25/Ni7/Cu75Ni25"},{"text":"European Commission figures agree: 23.25 mm, 2.33 mm, 7.50 g","source":2,"locator":"€1 entry","quote":"€1 Diameter: 23.25mm. Thickness: 2.33mm. Weight: 7.50g. Shape: round. Colour: outer part yellow/inner white. Composition: outer nickel-brass/inner three layered. Edge: interrupted/milled."}],"sources":[{"id":1,"label":"Council Regulation (EU) No 729/2014 of 24 June 2014 on denominations and technical specifications of euro coins intended for circulation (codification), OJ L 194, 2.7.2014, p. 1; Annex I (text as adopted, via legislation.gov.uk)","url":"https://www.legislation.gov.uk/eur/2014/729/annex/I/adopted","type":"standard","verified":"2026-10-30, full text of Annex I (UK National Archives copy of the EU text as adopted; EUR-Lex was not reachable by script)"},{"id":2,"label":"European Commission, DG ECFIN. Common sides of euro coins (web page)","url":"https://economy-finance.ec.europa.eu/euro/euro-coins-and-notes/euro-coins/common-sides-euro-coins_en","type":"standard","verified":"2026-10-30, full page HTML"}],"imageRefs":[{"label":"European Commission, common side of the €1 coin (new design), web image","what":"Face-on €1: round outline, yellow outer ring, white inner disc; used for inner/outer ratio"}],"artNotes":"This is the main calibration coin, so the circle is exact and the true-size length is its diameter (23.25 mm). Both faces are blank.","artSimplifications":["Faces blank (no common or national side design)","Interrupted milled edge not shown (face-on)","Inner-disc diameter traced from a web image"],"plate":{"src":{"256":"plates/euro-coin/256.webp","640":"plates/euro-coin/640.webp","1600":"plates/euro-coin/1600.webp","full":"plates/euro-coin/full.webp"},"w":1426,"h":1406,"pxPerMm":59.1203,"a":[27.7,703],"b":[1402.3,703]}},{"id":"uk-pound-coin","kind":"reference-object","common":"£1 coin (12-sided)","scientific":"","group":"Reference objects","tags":[],"measure":"Diameter, maximum (point to point across opposite corners) of the 12-sided £1 coin","state":"unknown","valueMm":23.43,"confidence":"high","fact":"The 12-sided £1 coin is 23.43 mm across the corners and 23.03 mm across the flats. Its sides are slightly curved ('radial chords') because a coin with flat sides and sharp corners rolled badly in coin-handling equipment.","marginNote":"The Royal Mint's answer to squaring the circle.","claims":[{"text":"Diameter 23.43 mm, thickness 2.80 mm, weight 8.75 g; first issued 28 March 2017","source":1,"locator":"Specification block for the 12-sided £1","quote":"First Issued 28th March 2017 Diameter 23.43mm Weight 8.75g Thickness 2.80mm Composition Outer Composition - Nickel-Brass Inner Composition - Nickel plated brass alloy"},{"text":"23.43 mm is the maximum, point-to-point diameter; edge to edge it is 23.03 mm","source":2,"locator":"p. 1, 'Coin Specification' box","quote":"Diameter: Maximum (point to point) 23.43mm; minimum (edge to edge) 23.03mm"},{"text":"12-sided with rounded edges ('radial chords') and rounded corners","source":2,"locator":"p. 1, 'Coin Specification' box","quote":"Shape: 12-sided with rounded edges (‘radial chords’) and corners"},{"text":"Rounded edges were introduced because a flat-sided, sharp-cornered 12-sided coin rolled badly in coin-handling equipment","source":3,"locator":"§3.6, PDF p. 13","quote":"Testing conducted by The Royal Mint, in partnership with a number of respondents, confirmed that these reservations were well-grounded for a 12-sided coin with flat sides and sharp corners. However, the introduction of rounded edges (‘radial chords’) to the design led to a significant improvement in its rolling behaviour, to a level consistent with that required by existing equipment."},{"text":"The government's 2015 'final specification' gave 23.5 mm point-to-point and 22.7 mm edge-to-edge, which differ from the coin as issued","source":3,"locator":"Box 2.A, PDF p. 12","quote":"Diameter: Maximum (point-to-point) 23.5mm; minimum (edge-to-edge) 22.7mm"}],"sources":[{"id":1,"label":"The Royal Mint. £1 Coin Designs and Specifications (web page)","url":"https://www.royalmint.com/discover/uk-coins/coin-design-and-specifications/one-pound-coin/","type":"standard","verified":"2026-10-30, full page HTML"},{"id":2,"label":"The Royal Mint (c. 2016) The New £1 Coin: Delivering Industry Readiness (industry flyer, 2 pp.); copy hosted by John Gaunt & Partners","url":"https://www.john-gaunt.co.uk/docs/New%201%20Coin%20Industry%20Flyer.pdf","type":"other","verified":"2026-10-30, full text (Royal Mint-branded PDF on a third-party host)"},{"id":3,"label":"HM Treasury (2015) Specification of the new £1 coin: response to the consultation","url":"https://www.gov.uk/government/consultations/specification-of-the-new-one-pound-coin","type":"other","verified":"2026-10-30, full text PDF"}],"imageRefs":[{"label":"Royal Mint industry flyer, p. 1 coin photograph","what":"Face-on photo of the 12-sided £1: outline, rounded corners and edges, gold outer ring / silver inner disc"}],"artNotes":"The true-size length runs corner to opposite corner (23.43 mm). The outline has 12 slightly convex sides and softened corners, and the faces are plain.","artSimplifications":["Faces left blank (no portrait or reverse design)","Milled edge not shown (face-on)","Inner/outer boundary diameter traced from a photo"],"plate":{"src":{"256":"plates/uk-pound-coin/256.webp","640":"plates/uk-pound-coin/640.webp","1600":"plates/uk-pound-coin/1600.webp","full":"plates/uk-pound-coin/full.webp"},"w":1398,"h":1378,"pxPerMm":57.8986,"a":[17.7,688],"b":[1374.3,688]}},{"id":"us-quarter-coin","kind":"reference-object","common":"US quarter (25¢)","scientific":"","group":"Reference objects","tags":[],"measure":"Coin diameter (US quarter dollar, round)","state":"unknown","valueMm":24.26,"confidence":"high","fact":"The US Mint gives the quarter as 24.26 mm across, 1.75 mm thick and 5.670 g, with 119 reeds round the edge. Under the silver-coloured faces it is mostly copper, since federal law makes it a copper core between two layers of 75% copper and 25% nickel.","marginNote":"Its diameter is written into federal law to a thousandth of an inch, which is more precision than most people bring to measuring anything else on this site.","claims":[{"text":"Diameter 0.955 in (24.26 mm), weight 5.670 g, thickness 1.75 mm","source":1,"locator":"Coin specifications table, rows 'Weight', 'Diameter', 'Thickness', 'Quarter Dollar' column","quote":"Denomination Cent Nickel Dime Quarter Dollar Half Dollar Dollar … Weight 2.500 g 5.000 g 2.268 g 5.670 g 11.340 g 8.1 g Diameter 0.750 in. 19.05 mm 0.835 in. 21.21 mm 0.705 in. 17.91 mm 0.955 in. 24.26 mm 1.205 in. 30.61 mm 1.043 in. 26.49 mm Thickness 1.52 mm 1.95 mm 1.35 mm 1.75 mm 2.15 mm 2.00 mm"},{"text":"Reeded edge with 119 reeds","source":1,"locator":"Coin specifications table, rows 'Edge' and 'No. of Reeds', 'Quarter Dollar' column","quote":"Edge Plain Plain Reeded Reeded Reeded Edge-Lettering No. of Reeds N/A N/A 118 119 150 N/A"},{"text":"Overall composition cupronickel, 8.33% nickel, balance copper","source":1,"locator":"Coin specifications table, 'Composition' row, 'Quarter Dollar' column","quote":"Composition Copper Plated Zinc 2.5% Cu Balance Zn Cupro-Nickel 25% Ni Balance Cu Cupro-Nickel 8.33% Ni Balance Cu Cupro-Nickel 8.33% Ni Balance Cu Cupro-Nickel 8.33% Ni Balance Cu Manganese-Brass 88.5% Cu 6% Zn 3.5% Mn 2% Ni"},{"text":"Federal law sets the quarter at 0.955 inch in diameter and 5.67 grams","source":2,"locator":"31 U.S.C. §5112(a)(3)","quote":"(3) a quarter dollar coin that is 0.955 inch in diameter and weighs 5.67 grams."},{"text":"The quarter is a three-layer clad coin: two outer layers of 75% copper and 25% nickel bonded to a copper inner layer","source":2,"locator":"31 U.S.C. §5112(b)","quote":"The half dollar, quarter dollar, and dime coins are clad coins with 3 layers of metal. The 2 identical outer layers are an alloy of 75 percent copper and 25 percent nickel. The inner layer is copper."}],"sources":[{"id":1,"label":"United States Mint. Coin Specifications (web page, content last updated 24 September 2019); read via the UNT Libraries Web Archive capture of 18 December 2020","url":"https://webarchive.library.unt.edu/web/20201218003308/https://www.usmint.gov/learn/coin-and-medal-programs/coin-specifications","type":"standard","verified":"2026-10-30, full page HTML of the archived copy (the live usmint.gov page returns a bot check to scripts, which was not bypassed)"},{"id":2,"label":"31 U.S.C. §5112, Denominations, specifications, and design of coins (text via Cornell Legal Information Institute)","url":"https://www.law.cornell.edu/uscode/text/31/5112","type":"standard","verified":"2026-10-30, full text of §5112(a) and (b)"},{"id":3,"label":"United States Mint. 2021-P Washington quarter, obverse (official coin image; public-domain copy on Wikimedia Commons, 768 × 768 px)","url":"https://commons.wikimedia.org/wiki/File:2021-P_US_Quarter_Obverse.jpg","type":"other","verified":"2026-10-30, image downloaded and measured"}],"imageRefs":[{"label":"US Mint, 2021-P quarter obverse (official image)","what":"Face-on quarter: round outline, raised rim, silver-coloured cupronickel face; used for the rim width"}],"artNotes":"The circle is exact and the true-size length is the diameter (24.26 mm). Both faces are left blank, and the thin raised rim is drawn at the width measured on a US Mint photo.","artSimplifications":["Faces blank (no Washington portrait, reverse design or lettering)","Reeded edge not shown (face-on)","Rim width traced from a photo"],"plate":{"src":{"256":"plates/us-quarter-coin/256.webp","640":"plates/us-quarter-coin/640.webp","1600":"plates/us-quarter-coin/1600.webp","full":"plates/us-quarter-coin/full.webp"},"w":1355,"h":1360,"pxPerMm":54.5177,"a":[16.7,679.3],"b":[1339.3,679.3]}},{"id":"argonaut","kind":"specimen","common":"Greater Argonaut","scientific":"Argonauta argo","group":"Molluscs","tags":["detachable","relative-champion"],"measure":"Total hectocotylus length (sucker-bearing part 8–10 lines plus filiform appendage 'about as much'), in three males whose arm was freed from its sac. Converted at 1 Paris line = 2.256 mm (assumed unit); range 16–20 lines = 36.1–45.1 mm","state":"dissected","valueMm":40.6,"rangeMm":[36.1,45.1],"recordMm":54.1,"bodyMm":9,"bodyMeasure":"Male body plus head to the base of the arms, about 4 lines (Paris line assumed), in the same three males","confidence":"low","fact":"The male's mating arm develops coiled in a sac and is made to break off. Found loose inside females, it was first described as a separate creature, until Müller found one still attached to a male.","marginNote":"He sends a representative.","claims":[{"text":"The detached hectocotylus was described as a separate creature before Müller found it attached to a male as one of its arms","source":2,"locator":"pp. 52–53","quote":"It is well known that Kolliker has endeavoured to show that the Hectocotylus of the Argonaut, described by Delle Chiaje and afterwards by Costa, is the male of this Cephalopod"},{"text":"Müller found the hectocotylus developing as one of the male's arms","source":2,"locator":"p. 52","quote":"I believe that in the present essay I for the first time describe the perfect male Argonaut, as one of the arms of which the so-called Hectocotylus Argonautæ is developed."},{"text":"The arm develops coiled inside a sac","source":2,"locator":"p. 54","quote":"In all cases a Hectocotylus Argonautæ lay coiled up within the sac."},{"text":"The hectocotylus is designed to detach; all those found loose were with female argonauts","source":2,"locator":"p. 56","quote":"The case here cited hardly allows us to doubt that the Hectocotylus once formed is intended to become detached from the rest of the animal ; as might indeed already be concluded from the fact that all the Hectocotyli seen by Delle Chiaje, Costa and Kolliker, to which I can add thirteen others, were found separated and associated with female Argonauts."},{"text":"Two parts: a thick sucker-bearing part and a thin, sucker-less filament","source":2,"locator":"p. 56","quote":"the one thick, and carrying suckers ; the other called by Kolliker the filiform appendage, thin and suckerless, but directly continuous with the former."},{"text":"Females are up to 10 to 15 times larger than males; the hectocotylus self-amputates","source":3,"locator":"p. 225 (Family Argonautidae, Diagnostic Features)","quote":"Sexual dimorphism very marked, with adult females relatively large, up to 10 to 15 times larger than adult males; hectocotylus of males autotomous (self-amputating)"},{"text":"Females: shell up to 30 cm, mantle up to 12 cm; males only 1.5 to 2 cm in total length","source":3,"locator":"p. 226 (Argonauta argo, Size)","quote":"Maximum length of shell to 30 cm in females; mantle to 12 cm; males are of dwarf size, only 1.5 to 2 cm in total length."},{"text":"A. argo males mature at 8 mm mantle length; males die soon after their first mating","source":4,"locator":"Family Argonautidae, Biology","quote":"Argonauta argo males mature at 8 mm ML (Naef 1923). No data are available on males of A. nodosa . The hectocotylus is lost during mating, and all males die soon after their first mating (Nesis 1977)."},{"text":"Sac colour: intense reddish brown when the pigment cells (chromatophores) are expanded, greyish when contracted","source":2,"locator":"p. 54","quote":"The colour, like that of the rest of the body, was intensely reddish brown when the chromatophora were dilated, more greyish when they were contracted."}],"sources":[{"id":1,"label":"Müller H. (1853) Ueber das Männchen von Argonauta Argo und die Hectocotylen. Zeitschrift für wissenschaftliche Zoologie 4:1–35, Taf. I","url":"https://archive.org/details/zeitschriftfrw04zeit","type":"peer-reviewed","verified":"2026-10-30, full text (Internet Archive scan; p. 5 checked on page image)"},{"id":2,"label":"Müller H. (1853) Upon the male of Argonauta argo and the Hectocotyli. In: Henfrey A., Huxley T.H. (eds) Scientific Memoirs, Natural History. London: Taylor & Francis, pp. 52–ff. (English translation of source 1)","url":"https://archive.org/details/scientificmemoir00henfrich","type":"book","verified":"2026-10-30, full text (Internet Archive OCR)"},{"id":3,"label":"Roper C.F.E., Sweeney M.J., Nauen C.E. (1984) FAO Species Catalogue Vol. 3. Cephalopods of the world. FAO Fisheries Synopsis 125(3), pp. 225–226 (Argonautidae)","url":"https://www.fao.org/4/ac479e/ac479e36.pdf","type":"monograph","verified":"2026-10-30, full text (FAO PDF)"},{"id":4,"label":"Australian Faunal Directory: Family Argonautidae (Australian Biological Resources Study, Department of Climate Change, Energy, the Environment and Water)","url":"https://biodiversity.org.au/afd/taxa/ARGONAUTIDAE","type":"museum","verified":"2026-10-30, full web page"}],"imageRefs":[{"label":"Müller 1853, Taf. I, Fig. 2","what":"Male A. argo with the hectocotylus freed from its sac: thick sucker-bearing arm continuing into a long, looping, thin filament; Fig. 1 shows a male with the arm still inside the sac"}],"artNotes":"The detached arm (hectocotylus) is laid out so its true-size length can be read along the centreline: the sucker-bearing part first, then the filament, which may loop. Converting to millimetres assumes the Paris line (see the confidence note), though the ratio to the male's body comes out the same whatever the unit. The record (54.1 mm or more) is a lower bound, from arms found loose in females, where Müller gives arm and filament about 27 mm each 'and more'. Arm and filament are drawn the same length because Müller's text says 'the appendage about as much'. His Taf. I Fig. 2 has the filament at about 1.6 times the sucker-bearing part, but the arm there is curled and its base is hard to place. Sucker count and the wave of the free end are schematic.","artSimplifications":["Sucker count not sourced; suckers drawn schematically","Pigment dots simplified","Shape traced from an 1853 coloured plate without a scale bar"],"plate":{"src":{"256":"plates/argonaut/256.webp","640":"plates/argonaut/640.webp","1600":"plates/argonaut/1600.webp","full":"plates/argonaut/full.webp"},"w":2257,"h":379,"pxPerMm":65.5138,"a":[73,129.5],"b":[2231.5,346],"path":[[73,129.5],[92.6,126.1],[112.4,122.9],[132,119.6],[151.6,116.4],[171.4,113.2],[191,110],[210.8,106.8],[230.4,103.7],[250.2,100.8],[270,97.9],[289.7,95],[309.5,92.2],[329.3,89.5],[349,86.9],[368.8,84.4],[388.5,82],[408.3,79.8],[428.2,77.7],[448.1,75.8],[467.9,73.8],[487.8,72.1],[507.7,70.5],[527.6,69.1],[547.5,67.8],[567.4,66.7],[587.3,65.7],[607.2,65],[627.1,64.3],[647.2,63.9],[667.1,63.7],[687,63.5],[707,63.7],[727,63.9],[746.9,64.3],[766.8,65],[786.8,65.7],[806.7,66.7],[826.6,67.8],[846.5,69.2],[866.4,70.7],[886.3,72.3],[906.1,74.1],[926,76.2],[945.8,78.3],[965.7,80.5],[985.4,83],[1005.2,85.5],[1025,88.1],[1044.7,91.1],[1064.5,94],[1084.1,97],[1103.9,100.3],[1123.5,103.6],[1143.2,106.9],[1162.8,110.4],[1182.4,114],[1202,117.6],[1221.7,121.4],[1241.1,125.2],[1260.8,129.1],[1280.4,133],[1299.9,136.8],[1319.4,140.9],[1339,144.9],[1358.5,148.8],[1378,152.9],[1394.4,156.3],[1404,158.3],[1413.8,160.4],[1423.7,162.3],[1433.3,164.4],[1443.1,166.4],[1452.8,168.4],[1462.6,170.4],[1472.4,172.5],[1482.1,174.4],[1491.9,176.5],[1501.7,178.5],[1511.4,180.5],[1521.2,182.5],[1531,184.6],[1540.7,186.7],[1550.5,188.6],[1560.3,190.7],[1570,192.7],[1579.8,194.7],[1589.6,196.7],[1599.3,198.8],[1609.1,200.7],[1618.9,202.8],[1628.6,204.8],[1638.4,206.8],[1648.2,208.8],[1657.9,210.9],[1667.7,212.8],[1677.5,214.9],[1687.2,216.9],[1697,219],[1706.8,220.9],[1716.5,222.9],[1726.5,224.2],[1736.4,224.9],[1746.4,224.9],[1756.3,224.2],[1766.1,222.9],[1775.9,220.8],[1785.5,218],[1794.9,214.5],[1803.8,210.3],[1812.7,205.6],[1820.9,200.2],[1828.8,194],[1836.1,187.2],[1842.8,180],[1848.8,172.1],[1854,163.7],[1858.5,154.8],[1862,145.5],[1864.5,136],[1866.1,126.1],[1866.4,116.3],[1865.4,106.4],[1863,96.8],[1859.3,87.6],[1854.3,79.1],[1847.9,71.6],[1840.3,65.2],[1831.6,60.3],[1822.2,57.1],[1812.2,55.7],[1802.3,56.3],[1792.6,58.6],[1783.5,62.7],[1775.2,68.1],[1767.8,74.8],[1761.6,82.4],[1756.5,90.9],[1752.4,100],[1749.4,109.4],[1747.6,119.2],[1746.8,128.9],[1747.1,138.9],[1748.3,148.7],[1750.4,158.4],[1753.4,167.9],[1757.2,176.9],[1761.8,185.8],[1767,194.2],[1772.9,202.3],[1779.3,209.8],[1786.3,216.7],[1793.9,223.3],[1801.9,229.3],[1810.3,234.5],[1819,239.3],[1828.1,243.4],[1837.3,246.9],[1846.9,249.7],[1856.7,252.1],[1866.2,255],[1875.3,259],[1883.9,263.9],[1892.3,269.3],[1900.1,275.3],[1907.8,281.6],[1915.6,288],[1923.1,294.5],[1930.7,300.9],[1938.4,307],[1946.5,313],[1954.8,318.5],[1963.5,323.3],[1972.5,327.4],[1982,330.6],[1991.7,332.8],[2001.6,333.9],[2011.6,334],[2021.5,333.3],[2031.4,332],[2041.2,330.1],[2051,327.9],[2060.5,325.4],[2070.2,322.9],[2079.9,320.3],[2089.5,317.9],[2099.2,315.7],[2109,314],[2119,312.6],[2128.9,312.1],[2138.9,312.1],[2148.8,312.9],[2158.6,314.4],[2168.3,316.9],[2177.8,320],[2187.1,323.6],[2196.2,327.6],[2205,332.1],[2213.9,336.7],[2222.7,341.3],[2231.5,346],[2231.5,346]]},"portrait":{"src":{"256":"portraits/argonaut/256.webp","640":"portraits/argonaut/640.webp","1200":"portraits/argonaut/1200.webp"},"w":1268,"h":1101,"alt":"A male greater argonaut, a small octopus with no shell, drawn side-on.","credit":"Drawn after Müller (1853), Taf. I, fig. 1."}},{"id":"leopard-slug","kind":"specimen","common":"Leopard Slug","scientific":"Limax maximus","group":"Molluscs","tags":["relative-champion"],"measure":"Length of the everted organ at the early club-shaped stage, before the frill unrolls; from measured field sketches of pairs hanging from mucus threads (midpoint of 1½–1¾ in, 38.1–44.5 mm)","state":"everted","valueMm":41.3,"rangeMm":[38.1,44.5],"bodyMm":150,"bodyMeasure":"Body length of British adults (midpoint of 10–20 cm); different author and population from the penis measurement","confidence":"low","fact":"Leopard slugs mate hanging in mid-air from a thick rope of mucus, their milk-white penes twisted together beneath them.","marginNote":"Their courtship calls for a rope, and the slugs have the good manners to bring their own.","claims":[{"text":"The pair lowers itself on a thick mucus strand about 38–46 cm long","source":1,"locator":"p. 92","quote":"Then, suddenly, the slugs intertwine fiercely, and launch themselves into space, heads downwards, but suspended by a thick strand of mucus, for the distance of 15—18 inches."},{"text":"The everted organs are milk white","source":1,"locator":"p. 93","quote":"The colour of the extruded organs is milk white, flecked here and there with dead white."},{"text":"The organs entwine into a knot whose upper whorls spread out like an umbrella","source":1,"locator":"p. 93","quote":"The two upper whorls of the knot thus formed now spread out in the form of a mushroom or umbrella, leaving the lower portion of the knot as before (fig. 9)."},{"text":"No penetration takes place in L. maximus","source":1,"locator":"p. 95","quote":"In the case of these latter, actual penetration takes place, which is not the case with Limax maximus"},{"text":"After mating, a slug often climbs back up the mucus thread, eating it as it goes","source":1,"locator":"p. 93","quote":"picks up the supporting thread in its mouth from the centre of its own footsole and climbs up to the point of support, eating the thread as it goes."},{"text":"Measurements came from carefully measured sketches made on the spot of a dozen or more examples","source":1,"locator":"p. 92","quote":"I may mention that my figures (kindly drawn by my friend, Mr. J. W. Taylor) are all from carefully-measured sketches on the spot, and that, though I have made drawings of a dozen or more examples, in no case did the measurements vary materially."},{"text":"L. maximus mates hanging in mid-air from a stout mucus thread; its entwined penes are shorter than those of L. cinereoniger","source":2,"locator":"p. 193 (L. maximus, Mating)","quote":"Unlike L, cinereoniger, L. maximus hangs suspended in mid-air from a stout thread of mucus. The protrusion of the organs, sperm transfer, and withdrawal of the penes is as in L. cinereoniger, but the entwined penes are not so long."},{"text":"In the related ash-black slug L. cinereoniger, the everted penes become as long as the body","source":2,"locator":"p. 190 (L. cinereoniger, Mating)","quote":"Their bodies and the evaginated penes, which become as long as the bodies, are entwined."}],"sources":[{"id":1,"label":"Adams L.E. (1898) Observations on the pairing of Limax maximus L. Journal of Conchology 9(3):92–95, Pl. III","url":"https://archive.org/details/journalofconchol918981900conc","type":"peer-reviewed","verified":"2026-10-30, full text (Internet Archive scan; fractions read from the page image because the OCR garbled them)"},{"id":2,"label":"Quick H.E. (1960) British slugs (Pulmonata; Testacellidae, Arionidae, Limacidae). Bulletin of the British Museum (Natural History) Zoology 6(3):103–226","url":"https://archive.org/details/biostor-1305","type":"monograph","verified":"2026-10-30, full text (BioStor PDF)"}],"imageRefs":[{"label":"Adams 1898, Plate III (drawn by J. W. Taylor from Adams's measured sketches)","what":"Figs 1–4: everted organ as a club (fig. 1), with frill appearing (fig. 2), fully unrolled (fig. 3) and entwining (fig. 4); figs 5–9: knot and umbrella; fig. 9: whole pair hanging from the mucus thread"}],"artNotes":"Shows the early club-shaped stage (Pl. III fig. 1), which is the stage the 1½–1¾ in (38–44 mm) measurement describes. The later stage, with the two penes entwined (figs 5–9), is left out because it would not match the measurement. The source plate has no scale bar, so proportions are approximate.","artSimplifications":["Single organ shown, not the entwined pair","Dead-white flecks simplified"],"plate":{"src":{"256":"plates/leopard-slug/256.webp","640":"plates/leopard-slug/640.webp","1600":"plates/leopard-slug/1600.webp","full":"plates/leopard-slug/full.webp"},"w":2273,"h":494,"pxPerMm":53.4128,"a":[43.6,248],"b":[2249.7,248]},"portrait":{"src":{"256":"portraits/leopard-slug/256.webp","640":"portraits/leopard-slug/640.webp","1200":"portraits/leopard-slug/1200.webp"},"w":2323,"h":524,"alt":"A leopard slug, drawn side-on.","credit":"Drawn after a photo by Didier Descouens (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"aa-battery","kind":"reference-object","common":"AA battery (LR6)","scientific":"","group":"Reference objects","tags":[],"measure":"Overall length including positive terminal (midpoint of the 49.50–50.50 mm industry-standard range for IEC LR6 / ANSI 15A)","state":"unknown","valueMm":50,"rangeMm":[49.5,50.5],"confidence":"high","fact":"Within the standard, an AA (IEC LR6) cell can be 49.5–50.5 mm in length and 13.5–14.5 mm in diameter, and its positive terminal no more than 5.5 mm across.","marginNote":"For once the battery is included, which is more than most toys can say on Christmas morning.","claims":[{"text":"Designation ANSI-15A, IEC-LR6","source":1,"locator":"p. 1, Specifications","quote":"Designation: ANSI-15A, IEC-LR6"},{"text":"Length 49.50–50.50 mm","source":1,"locator":"p. 1, 'Industry Standard Dimensions' drawing","quote":"50.50 (1.988) 49.50 (1.949)"},{"text":"Diameter 13.50–14.50 mm","source":1,"locator":"p. 1, 'Industry Standard Dimensions' drawing","quote":"14.50 (0.571) 13.50 (0.531)"},{"text":"Positive terminal diameter at most 5.50 mm; terminal projection at least 1.00 mm","source":1,"locator":"p. 1, drawing","quote":"5.50 (0.217) Maximum … 1.00 (0.039) Minimum"},{"text":"Negative contact at least 7.00 mm across","source":1,"locator":"p. 1, drawing","quote":"7.00 (0.276) Minimum"},{"text":"Typical weight 23.0 g","source":1,"locator":"p. 1, Specifications","quote":"Typical Weight: 23.0 grams (0.8 oz.)"}],"sources":[{"id":1,"label":"Energizer Brands, LLC. Energizer E91 AA product datasheet (Form No. EBC-1102-R); copy hosted by Connectec","url":"https://cdn.connectec.uk/Files/Products/Batteries/energizer_batteries/e91_aa_battery_datasheet.pdf","type":"other","verified":"2026-10-30, full text (manufacturer PDF; identical figures in the University of Houston-hosted E91 copy and the EN91 datasheet)"}],"imageRefs":[{"label":"Energizer E91 datasheet, 'Industry Standard Dimensions' drawing","what":"Side elevation of the AA cell with positive button, negative end and dimension callouts"}],"artNotes":"Measured overall, from the tip of the positive button to the flat negative end. We left off the brand, the printing and the + and − marks.","artSimplifications":["Unbranded plain wrapper","Terminal details simplified to a button and a flat end"],"plate":{"src":{"256":"plates/aa-battery/256.webp","640":"plates/aa-battery/640.webp","1600":"plates/aa-battery/1600.webp","full":"plates/aa-battery/full.webp"},"w":2437,"h":718,"pxPerMm":47.5317,"a":[29,358.5],"b":[2405.6,358.5]}},{"id":"drosophila-bifurca","kind":"specimen","common":"Giant-sperm fruit fly (sperm, not a penis)","scientific":"Drosophila bifurca","group":"Insects","tags":["record-holder"],"measure":"Sperm length (uncoiled), whole spermatozoon; mean of 3–5 males (sperm cell, not a penis)","state":"unknown","valueMm":58.29,"confidence":"medium","fact":"Uncoiled, a single sperm of this fruit fly averages 58.29 mm. Males need 17 days after emerging to produce fertile sperm; females are ready at 7.","marginNote":"Off topic, admittedly.","claims":[{"text":"Mean sperm length of D. bifurca is 58.29 mm (3–5 males measured)","source":1,"locator":"p.10615, Fig. 1 data table; Methods p.10614","quote":"D. bifurca 58.29 ± 0.67(4) 7(4) 17(4) 1.65 ± 0.00 1.60 ± 0.00"},{"text":"Same value reported again in 2006 (citing Pitnick, Spicer & Markow 1995)","source":2,"locator":"p.742, main text; Table 1 (p.743)","quote":"D. bifurca (sperm length ¼ 58.29 mm; GSI ¼ 10.60; ref. 25)"},{"text":"A single ~6 cm spermatozoon; in the seminal vesicle the sperm are individually rolled into compact balls","source":2,"locator":"p.743, Figure 1 caption","quote":"a, Scanning electron micrograph (SEM) showing a single, 6-cm D. bifurca spermatozoon dissected from the seminal vesicle, where sperm are individually rolled into compact balls."},{"text":"Males take 17 days after emerging to produce fertile gametes; females take 7","source":2,"locator":"p.742, main text","quote":"males require 17 days posteclosion to produce fertile gametes, whereas females require only 7 days (ref. 25)"},{"text":"Some Drosophila species make sperm more than 10 times the male's total body length","source":1,"locator":"p.10614, Abstract","quote":"Among fruit-fly species of the genus Drosophila there is remarkable variation in sperm length, with some species producing gigantic sperm (e.g., >10 times total male body length)."},{"text":"Across 42 Drosophila species sperm length ranged from 0.32 to 58.3 mm (D. bifurca is the top of the range)","source":1,"locator":"p.10616, Discussion","quote":"sperm length (range: 0.32-58.3 mm; Fig. 1)"},{"text":"D. bifurca is nearly isogamous: sperm are made only about six times faster than eggs","source":2,"locator":"p.742, main text; Figure 1 caption","quote":"D. bifurca is nearly isogamous in terms of gamete size and gamete production rate (Fig. 1)."},{"text":"Only a tiny portion of the sperm enters the egg","source":2,"locator":"p.743, main text","quote":"For example, in D. bifurca only a tiny portion of the sperm enters the egg; the vast majority is used neither by the egg nor the female27."},{"text":"Male thorax length 1.6 mm (thorax only; no total body length sourced)","source":1,"locator":"p.10615, Fig. 1 (data table: 'Thorax length, mm', Females / Males)","quote":"D. bifurca 58.29 ± 0.67(4) 7(4) 17(4) 1.65 ± 0.00 1.60 ± 0.00"}],"sources":[{"id":1,"label":"Pitnick S., Markow T.A., Spicer G.S. (1995) Delayed male maturity is a cost of producing large sperm in Drosophila. Proc. Natl. Acad. Sci. USA 92:10614–10618","doi":"10.1073/pnas.92.23.10614","url":"https://www.pnas.org/doi/10.1073/pnas.92.23.10614","type":"peer-reviewed","verified":"2026-10-30, full text read (PDF via Wayback Machine copy of pnas.org/content/pnas/92/23/10614.full.pdf); the (4) beside the D. bifurca values is a reference marker to Pitnick, Spicer & Markow 1995 Nature 375:109"},{"id":2,"label":"Bjork A., Pitnick S. (2006) Intensity of sexual selection along the anisogamy–isogamy continuum. Nature 441:742–745","doi":"10.1038/nature04683","url":"https://zenodo.org/records/1000855","type":"peer-reviewed","verified":"2026-10-30, full text read (Zenodo open copy of the published PDF); '¼' in quotes is the PDF's rendering of '='"}],"imageRefs":[{"label":"Bjork & Pitnick 2006, Nature 441, Fig. 1a","what":"SEM of one whole D. bifurca spermatozoon (~6 cm) as a loose tangle of a single uniform filament (scale bar 20 µm)"},{"label":"Bjork & Pitnick 2006, Nature 441, Fig. 1b","what":"A single sperm rolled into a compact ball (shown six times) beside the much larger egg, same magnification (scale bar 50 µm)"}],"artNotes":"Inside the body the 58.29 mm sperm is wound into a tangle about 0.1 mm across (Bjork & Pitnick 2006 Fig. 1a). The plate uncoils it into a shallow wave whose arc length is 58.29 mm; the shape of the wave is ours. No head is drawn, and the filament is far thicker than life so that it can be seen at all.","artSimplifications":["Filament width exaggerated so it is visible (true width not sourced)","Loop count and arrangement illustrative","Head/tail differentiation omitted"],"plate":{"src":{"256":"plates/drosophila-bifurca/256.webp","640":"plates/drosophila-bifurca/640.webp","1600":"plates/drosophila-bifurca/1600.webp","full":"plates/drosophila-bifurca/full.webp"},"w":2434,"h":322,"pxPerMm":58.9489,"a":[27.4,162],"b":[2404.6,146.1],"path":[[27.4,162],[33.4,152.8],[39.2,143.7],[45.1,134.6],[51,125.7],[56.8,117.1],[62.8,108.5],[68.7,100.4],[74.5,92.3],[80.5,84.8],[86.4,77.6],[92.2,70.7],[98.2,64.4],[104.1,58.5],[109.9,53.1],[115.9,48.2],[121.8,43.9],[127.6,40.2],[133.5,37],[139.5,34.6],[145.3,32.6],[151.2,31.3],[157.2,30.7],[163,30.7],[168.9,31.3],[174.9,32.6],[180.7,34.6],[186.6,37],[192.4,40.2],[198.3,43.9],[204.3,48.2],[210.1,53.1],[216,58.5],[222,64.4],[227.8,70.7],[233.7,77.6],[239.7,84.8],[245.5,92.3],[251.4,100.4],[257.3,108.5],[263.2,117.1],[269.1,125.7],[275,134.6],[280.8,143.7],[286.8,152.8],[292.7,162],[298.5,171.2],[304.5,180.3],[310.4,189.4],[316.2,198.3],[322.2,206.9],[328.1,215.5],[333.9,223.6],[339.8,231.7],[345.8,239.2],[351.6,246.4],[357.5,253.3],[363.5,259.6],[369.3,265.5],[375.2,270.9],[381.2,275.8],[387,280.1],[392.9,283.8],[398.8,287],[404.6,289.4],[410.6,291.4],[416.5,292.7],[422.3,293.3],[428.3,293.3],[434.2,292.7],[440,291.4],[446,289.4],[451.9,287],[457.7,283.8],[463.7,280.1],[469.6,275.8],[475.4,270.9],[481.3,265.5],[487.3,259.6],[493.1,253.3],[499,246.4],[504.8,239.2],[510.8,231.7],[516.7,223.6],[522.5,215.5],[528.5,206.9],[534.4,198.3],[540.2,189.4],[546.1,180.3],[552.1,171.2],[557.9,162],[563.8,152.8],[569.8,143.7],[575.6,134.6],[581.5,125.7],[587.5,117.1],[593.3,108.5],[599.2,100.4],[605.2,92.3],[611,84.8],[616.9,77.6],[622.8,70.7],[628.6,64.4],[634.6,58.5],[640.5,53.1],[646.3,48.2],[652.3,43.9],[658.2,40.2],[664,37],[670,34.6],[675.9,32.6],[681.7,31.3],[687.6,30.7],[693.6,30.7],[699.4,31.3],[705.3,32.6],[711.3,34.6],[717.1,37],[723,40.2],[729,43.9],[734.8,48.2],[740.7,53.1],[746.7,58.5],[752.5,64.4],[758.4,70.7],[764.3,77.6],[770.1,84.8],[776.1,92.3],[782,100.4],[787.8,108.5],[793.8,117.1],[799.7,125.7],[805.5,134.6],[811.5,143.7],[817.4,152.8],[823.2,162],[829.1,171.2],[834.9,180.3],[840.9,189.4],[846.8,198.3],[852.6,206.9],[858.6,215.5],[864.5,223.6],[870.3,231.7],[876.3,239.2],[882.2,246.4],[888,253.3],[894,259.6],[899.9,265.5],[905.7,270.9],[911.6,275.8],[917.6,280.1],[923.4,283.8],[929.3,287],[935.3,289.4],[941.1,291.4],[947,292.7],[953,293.3],[958.8,293.3],[964.7,292.7],[970.6,291.4],[976.4,289.4],[982.4,287],[988.3,283.8],[994.1,280.1],[1000.1,275.8],[1006,270.9],[1011.8,265.5],[1017.8,259.6],[1023.7,253.3],[1029.5,246.4],[1035.4,239.2],[1041.4,231.7],[1047.2,223.6],[1053.1,215.5],[1059.1,206.9],[1064.9,198.3],[1070.8,189.4],[1076.8,180.3],[1082.6,171.2],[1088.5,162],[1094.5,152.8],[1100.3,143.7],[1106.2,134.6],[1112.1,125.7],[1117.9,117.1],[1123.9,108.5],[1129.8,100.4],[1135.6,92.3],[1141.6,84.8],[1147.4,77.6],[1153.3,70.7],[1159.3,64.4],[1165.1,58.5],[1171,53.1],[1176.9,48.2],[1182.7,43.9],[1188.7,40.2],[1194.6,37],[1200.4,34.6],[1206.4,32.6],[1212.3,31.3],[1218.1,30.7],[1224.1,30.7],[1230,31.3],[1235.8,32.6],[1241.8,34.6],[1247.7,37],[1253.5,40.2],[1259.4,43.9],[1265.4,48.2],[1271.2,53.1],[1277.1,58.5],[1283.1,64.4],[1288.9,70.7],[1294.8,77.6],[1300.8,84.8],[1306.6,92.3],[1312.5,100.4],[1318.4,108.5],[1324.2,117.1],[1330.2,125.7],[1336.1,134.6],[1341.9,143.7],[1347.9,152.8],[1353.8,162],[1359.6,171.2],[1365.6,180.3],[1371.5,189.4],[1377.3,198.3],[1383.3,206.9],[1389.2,215.5],[1395,223.6],[1400.9,231.7],[1406.9,239.2],[1412.7,246.4],[1418.6,253.3],[1424.6,259.6],[1430.4,265.5],[1436.3,270.9],[1442.3,275.8],[1448.1,280.1],[1454,283.8],[1459.8,287],[1465.7,289.4],[1471.7,291.4],[1477.5,292.7],[1483.4,293.3],[1489.4,293.3],[1495.2,292.7],[1501.1,291.4],[1507.1,289.4],[1512.9,287],[1518.8,283.8],[1524.7,280.1],[1530.6,275.8],[1536.5,270.9],[1542.4,265.5],[1548.2,259.6],[1554.2,253.3],[1560.1,246.4],[1565.9,239.2],[1571.9,231.7],[1577.8,223.6],[1583.6,215.5],[1589.6,206.9],[1595.5,198.3],[1601.3,189.4],[1607.2,180.3],[1613.2,171.2],[1619,162],[1624.9,152.8],[1630.9,143.7],[1636.7,134.6],[1642.6,125.7],[1648.6,117.1],[1654.4,108.5],[1660.3,100.4],[1666.2,92.3],[1672,84.8],[1678,77.6],[1683.9,70.7],[1689.7,64.4],[1695.7,58.5],[1701.6,53.1],[1707.4,48.2],[1713.4,43.9],[1719.3,40.2],[1725.1,37],[1731.1,34.6],[1737,32.6],[1742.8,31.3],[1748.7,30.7],[1754.7,30.7],[1760.5,31.3],[1766.4,32.6],[1772.2,34.6],[1778.2,37],[1784.1,40.2],[1789.9,43.9],[1795.9,48.2],[1801.8,53.1],[1807.6,58.5],[1813.5,64.4],[1819.5,70.7],[1825.3,77.6],[1831.2,84.8],[1837.2,92.3],[1843,100.4],[1848.9,108.5],[1854.9,117.1],[1860.7,125.7],[1866.6,134.6],[1872.6,143.7],[1878.4,152.8],[1884.3,162],[1890.2,171.2],[1896,180.3],[1902,189.4],[1907.9,198.3],[1913.7,206.9],[1919.7,215.5],[1925.6,223.6],[1931.4,231.7],[1937.4,239.2],[1943.3,246.4],[1949.1,253.3],[1955,259.6],[1961,265.5],[1966.8,270.9],[1972.7,275.8],[1978.7,280.1],[1984.5,283.8],[1990.4,287],[1996.4,289.4],[2002.2,291.4],[2008.1,292.7],[2014,293.3],[2019.9,293.3],[2025.8,292.7],[2031.7,291.4],[2037.5,289.4],[2043.5,287],[2049.4,283.8],[2055.2,280.1],[2061.2,275.8],[2067.1,270.9],[2072.9,265.5],[2078.9,259.6],[2084.8,253.3],[2090.6,246.4],[2096.5,239.2],[2102.3,231.7],[2108.3,223.6],[2114.2,215.5],[2120,206.9],[2126,198.3],[2131.9,189.4],[2137.7,180.3],[2143.7,171.2],[2149.6,162],[2155.4,152.8],[2161.3,143.7],[2167.3,134.6],[2173.1,125.7],[2179,117.1],[2185,108.5],[2190.8,100.4],[2196.7,92.3],[2202.7,84.8],[2208.5,77.6],[2214.4,70.7],[2220.4,64.4],[2226.2,58.5],[2232.1,53.1],[2238,48.2],[2243.8,43.9],[2249.8,40.2],[2255.7,37],[2261.5,34.6],[2267.5,32.6],[2273.4,31.3],[2279.2,30.7],[2285.2,30.7],[2291.1,31.3],[2296.9,32.6],[2302.8,34.6],[2308.8,37],[2314.6,40.2],[2320.5,43.9],[2326.5,48.2],[2332.3,53.1],[2338.2,58.5],[2344.2,64.4],[2350,70.7],[2355.9,77.6],[2361.9,84.8],[2367.7,92.3],[2373.6,100.4],[2379.5,108.5],[2385.3,117.1],[2391.3,125.7],[2397.2,134.6],[2403,143.7],[2404.6,146.1]]},"signatureAnimation":"sperm-unspool","portrait":{"src":{"256":"portraits/drosophila-bifurca/256.webp","640":"portraits/drosophila-bifurca/640.webp","1200":"portraits/drosophila-bifurca/1200.webp"},"w":1137,"h":754,"alt":"A male Drosophila bifurca fruit fly, drawn side-on.","credit":"Drawn after a photo of its relative Drosophila hydei by Pogrebnoj-Alexandroff (Wikimedia Commons, CC BY 3.0)."}},{"id":"echidna","kind":"specimen","common":"Short-beaked Echidna","scientific":"Tachyglossus aculeatus","group":"Mammals","tags":["bifurcated","spines"],"measure":"Penis length (state not stated in source; 'about')","state":"unknown","valueMm":70,"bodyMm":425,"bodyMeasure":"Average adult length (midpoint of 400–450 mm)","confidence":"low","fact":"The glans has four rosette-tipped heads. Only two are used at once, and the left and right pairs take turns.","marginNote":"With four heads and only two in use at a time, it rotates them like a careful driver rotating tyres.","claims":[{"text":"Four rosettes; two retract while the other two engorge","source":3,"locator":"p.E162","quote":"During the early stages of erection, the glans penis displays all four rosettes, but as the erection continues, two of the rosettes retract, leaving the remaining rosettes fully engorged and slightly rotated, to give the fully erect penis a symmetrical appearance"},{"text":"Left and right sides used alternately in 10 consecutive ejaculations","source":3,"locator":"p.E163","quote":"10 consecutive observations of ejaculation revealed that the left and right sides of the glans were used alternately."},{"text":"About 70 mm long","source":5,"locator":"Ch. 15 Tachyglossidae, 'Male System', p. 31","quote":"The penis is about 70 mm long, dorso-ventrally compressed and with a bifid glans."},{"text":"Mostly smooth, with spines mainly around the glans","source":4,"locator":"PDF p.3","quote":"Most of the skin of the penis is relatively smooth with epithelial spines present mainly at the distal tip, surrounding the glans (Fig. 1h)."},{"text":"At rest the penis lies in a preputial sac and is forced out through the cloaca on erection","source":5,"locator":"Ch. 15 Tachyglossidae, 'Male System', p. 31","quote":"It lies within a thin-walled preputial sac located ventral to the cloaca. In the ventral wall of the latter is an opening through which the penis, upon erection, is forced into the cloaca and to the exterior through the cloacal sphincter (Fig. 15.8)."},{"text":"Rismiller & Grützner 2019 repeat the 70 mm figure, citing Griffiths 1978","source":1,"locator":"p.83","quote":"The penis, used solely for the passage of spermatozoa, is about 70 mm long and has a bifid glans with two openings on each glans (Griffiths 1978)."}],"sources":[{"id":1,"label":"Rismiller P.D., Grützner F. (2019) Tachyglossus aculeatus (Monotremata: Tachyglossidae). Mammalian Species 51(980):75–91","doi":"10.1093/mspecies/sez012","type":"monograph","verified":"2026-10-30, Plazi TreatmentBank text (page mapping from Plazi)"},{"id":3,"label":"Johnston S.D., Smith B., Pyne M., Stenzel D., Holt W.V. (2007) One-sided ejaculation of echidna sperm bundles. The American Naturalist 170(6):E162–E164","doi":"10.1086/522847","type":"peer-reviewed","verified":"2026-10-30, QUT ePrints author copy"},{"id":4,"label":"Fenelon J.C., McElrea C., Shaw G., Evans A.R., Pyne M., Johnston S.D., Renfree M.B. (2021) The unique penile morphology of the short-beaked echidna, Tachyglossus aculeatus. Sexual Development 15(4):262–271","doi":"10.1159/000515145","type":"peer-reviewed","verified":"2026-10-30, Minerva Access accepted version"},{"id":5,"label":"Griffiths M. (1989) Tachyglossidae. Chapter 15 in Walton D.W., Richardson B.J. (eds) Fauna of Australia, Vol. 1B Mammalia. Australian Government Publishing Service, Canberra","url":"https://www.dcceew.gov.au/sites/default/files/env/pages/a117ced5-9a94-4586-afdb-1f333618e1e3/files/15-ind.pdf","type":"monograph","verified":"2026-10-30, full chapter PDF read (DCCEEW chapter PDF via Wayback id_ copy of 2025-05-06; live server times out). Page numbers are those printed in the chapter PDF."}],"imageRefs":[{"label":"Johnston et al. 2007, Fig. 2A","what":"Erect lateral view: shaft, basal collar, Y of engorged rosettes, retracted pair (arrow)"},{"label":"Fenelon et al. 2021, Figs 1c, 1h, 3a","what":"Four-rosette cluster, distal spines, everted side view"},{"label":"Griffiths 1989 (FoA ch. 15), Fig. 15.8","what":"Male excretory and reproductive organs with the preputial sac removed to show the (resting) penis; after Griffiths 1968"},{"label":"Griffiths 1989 (FoA ch. 15), p. 31","what":"Page render of the 'Male System' text containing the 70 mm statement"}],"artNotes":"The length is uncertain. Griffiths (1989) gives about 70 mm without saying whether erect, while another estimate puts it at about a quarter of body length, roughly 100–113 mm. Proportions are traced from an unscaled photograph and the colour also comes from photographs, as no text describes it. Griffiths says the penis is flattened top to bottom, so from the side the shaft may look a little narrower than it would from above.","artSimplifications":["Papillae and pores simplified","Colour taken from photographs"],"plate":{"src":{"256":"plates/echidna/256.webp","640":"plates/echidna/640.webp","1600":"plates/echidna/1600.webp","full":"plates/echidna/full.webp"},"w":2097,"h":1072,"pxPerMm":27.9127,"a":[97.5,532.7],"b":[2051.4,532.7]},"signatureAnimation":"four-heads","portrait":{"src":{"256":"portraits/echidna/256.webp","640":"portraits/echidna/640.webp","1200":"portraits/echidna/1200.webp"},"w":1842,"h":1066,"alt":"A short-beaked echidna, drawn side-on.","credit":"Drawn after a photo by Charles J. Sharp (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"western-gorilla","kind":"specimen","common":"Western gorilla","scientific":"Gorilla gorilla","group":"Mammals","tags":["baculum"],"measure":"Dissected penis of one preserved gorilla, from the glans to where the corpora cavernosa diverge (Duvernoy 1855); age not stated","state":"dissected","valueMm":70,"bodyMm":1050,"bodyMeasure":"Adult male head-body length, midpoint of the stated range 103-107 cm (Western gorilla; not the same animal as the penis measurement)","confidence":"low","fact":"No sample of erect gorilla penises has ever been measured. The '3 cm' that keeps being repeated is an unreferenced estimate, and the one dissected specimen we know of measured about 7 cm.","marginNote":"Further volunteers have not come forward.","claims":[{"text":"The much-repeated '3 cm' figure comes from R. V. Short's 1981 review essay, which gives it with no sample size or method","source":2,"locator":"Ch. 13 (pp. 319-341), gorilla paragraph of the comparison of great-ape genitalia; exact page not recoverable from the full-text search","quote":"the flaccid penis is only about a centimeter long, and its black color blends with that of the surround- ing skin. The fully erect penis is only 3 cm in length and is in no way conspicuous."},{"text":"A dissected gorilla penis measured about 7 cm from the glans to where the corpora cavernosa diverge, about 12 mm in diameter near the glans and 25 mm near the pubis","source":3,"locator":"Troisième mémoire, ch. on male genital organs, §I 'De la verge', pp. 208-209","quote":"Cette verge est d’ailleurs petite, relativement au corps de lanimal. Son diamètre vers le gland n'excède pas o\"o12, et vers le pubis 0\"025. … Sa longueur, depuis le gland jusqu’à l’écartement des corps caverneux, n’est guère que de o\"o7."},{"text":"The glans is black and mushroom-shaped, with two rounded lobes either side of a wide vertical urethral slit; the shaft is narrow just behind the glans and widens rapidly into a cone","source":3,"locator":"pp. 208-209; Pl. XVI figs V-VII","quote":"Le gland est noir, largement fendu verticalement par l’orifice de l’urèthre, il présente deux lobes arrondis de chaque côté de cet orifice. Sur les côtés, et surtout en dessus, s’élève une large crête ridée, qui lui donne une forme de champignon. La verge proprement dite, est d’un petit diamètre, immédiatement derrière le gland ; ce diamètre va rapidement en augmentant, ce qui lui donne une forme conique."},{"text":"The shaft skin is wrinkled in all directions, mostly crosswise, and greyish, paler than the glans","source":3,"locator":"p. 208","quote":"La peau de cette partie, très-ridée en tous sens, mais surtout en travers, est de couleur grisâtre, moins foncée conséquemment que le gland."},{"text":"Owen (1865) described the gorilla penis as short and subconical","source":5,"locator":"p. 247 (text), Pl. XLVI fig. 2","quote":"In the male the penis (PI. XLVI. fig. 2) is short and subconical; the prepuce is devoid of frsenum"},{"text":"Gorillas have a penis bone (baculum) of about 12.5 mm","source":6,"locator":"Ch. 9, section 'The evolution of the baculum' (near Figs 9.8-9.9); page not recoverable from the full-text search","quote":"a longer baculum (14.6-15.0mm) than the gorilla (12.5 mm), chimpanzee (6.0—7.8 mm), or bonobo (8.6mm)"}],"sources":[{"id":2,"label":"Short R.V. (1981) Sexual selection in man and the great apes. In: Graham C.E. (ed.) Reproductive Biology of the Great Apes: Comparative and Biomedical Perspectives. Academic Press, New York, Ch. 13, pp. 319-341","doi":"10.1016/B978-0-12-295020-9.50019-4","url":"https://archive.org/details/reproductivebiol0000unse_h5d9","type":"book","verified":"2026-10-30, verbatim sentence fragments recovered via archive.org full-text search of the scanned book (lending-only item; page images not viewable). The paragraph cites Harcourt et al. (Ch. 10, 'Gorilla reproduction in the wild'), confirming it is the gorilla paragraph. Snippets saved in refs/short1981_fulltext_snippets.txt; exact page not available"},{"id":3,"label":"Duvernoy G.L. (1855-1856) Des caractères anatomiques des grands singes pseudo-anthropomorphes. Archives du Muséum d'Histoire Naturelle (Paris) 8:1-248, pls I-XVI (penis pp. 208-210, 227; Pl. XVI figs V-VII)","url":"https://archive.org/details/archivesdumusu08muse","type":"monograph","verified":"2026-10-30, full scanned volume (archive.org PDF and OCR text). Text extract in refs/duvernoy1855_pp208-210_penis.txt. Note: the specimen was a preserved adult male whose sheath and pelvic parts were damaged (Duvernoy says so); measurements are of the dissected organ"},{"id":4,"label":"Mittermeier R.A., Rylands A.B., Wilson D.E. (eds) (2013) Handbook of the Mammals of the World. Vol. 3, Primates. Lynx Edicions, Barcelona. Family Hominidae, pp. 792-854 (Gorilla gorilla account pp. 848-849)","url":"https://tb.plazi.org/GgServer/xhtml/03FA8785400C9F6FFF4EF71BFBBAB8F8","type":"monograph","verified":"2026-10-30, full species-account text via Plazi TreatmentBank (refs/plazi_gorilla_gorilla.html)"},{"id":5,"label":"Owen R. (1865) Contributions to the natural history of the anthropoid apes. No. VIII. On the external characters of the gorilla (Troglodytes gorilla, Sav.). Transactions of the Zoological Society of London 5:243-284, pls XLIII-XLVII","url":"https://archive.org/details/biostor-146005","type":"peer-reviewed","verified":"2026-10-30, full scanned article (archive.org/BioStor PDF), text and plates"},{"id":6,"label":"Dixson A.F. (1998) Primate Sexuality: Comparative Studies of the Prosimians, Monkeys, Apes, and Human Beings. Oxford University Press","url":"https://archive.org/details/primatesexuality0000dixs","type":"monograph","verified":"2026-10-30, verbatim fragment via archive.org full-text search only (lending item; page not viewable). refs/dixson1998_fulltext_snippets.txt"}],"imageRefs":[{"label":"Duvernoy 1855-56, Archives du Muséum 8, Pl. XVI figs V-VII","what":"Dissected adult gorilla penis: fig. V dorsal view of glans and conical shaft; fig. VI lateral profile of the glans and the black-skinned distal shaft; fig. VII glans end-on showing two lobes either side of the vertical urethral slit"},{"label":"Duvernoy 1855-56, Pl. XVI (whole plate) and caption","what":"Context: 'F. V. VI. VII. Verge du gorille'"},{"label":"Owen 1865, Trans. Zool. Soc. 5, Pl. XLVI fig. 2","what":"Preserved adult male lying supine; small subconical flaccid penis visible in the pubic hair (crop: refs/owen1865_plXLVI_fig2_crop.png)"}],"artNotes":"Nobody has described the erect shape, so the plate shows Duvernoy's dissected specimen of 1855: a cone 70 mm long, 25 mm wide at the base and 12 mm near the glans (all his measurements), with the glans profile traced from his Pl. XVI fig. VI. Owen's 1865 Pl. XLVI fig. 2 shows the same short, subconical shape in place in the body. The cross-wrinkles are stylised.","artSimplifications":["Shape from a dissected 1855 specimen, not an erect organ","Glans crest wrinkling stylised","Baculum not shown"],"plate":{"src":{"256":"plates/western-gorilla/256.webp","640":"plates/western-gorilla/640.webp","1600":"plates/western-gorilla/1600.webp","full":"plates/western-gorilla/full.webp"},"w":2418,"h":918,"pxPerMm":33,"a":[79.6,425.2],"b":[2389.6,425.2]},"portrait":{"src":{"256":"portraits/western-gorilla/256.webp","640":"portraits/western-gorilla/640.webp","1200":"portraits/western-gorilla/1200.webp"},"w":1623,"h":1542,"alt":"A silverback western gorilla, drawn side-on on his knuckles.","credit":"Drawn after a photo by Pbernd0910 (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"banana-slug","kind":"specimen","common":"Slender Banana Slug","scientific":"Ariolimax dolichophallus","group":"Molluscs","tags":["relative-champion"],"measure":"Penis length when relaxed and fully invaginated (dissected); midpoint of the 60–110 mm range in the original species description","state":"dissected","valueMm":85,"rangeMm":[60,110],"recordMm":110,"bodyMm":165,"bodyMeasure":"Foot length when fully extended, adults (midpoint of 150–180 mm); same species description","confidence":"medium","fact":"This slug was named dolichophallus after its penis, which is 'not infrequently' longer than the slug itself. Sometimes, at the end of mating, it gets chewed off.","marginNote":"The name was not subtle.","claims":[{"text":"The very long, thin end section of the penis is sometimes longer than the whole slug","source":1,"locator":"p. 690 (Remarks)","quote":"This new species is immediately identified by the extremely attenuate apical phallus which not infrequently is of greater length than the slug itself!"},{"text":"The name dolichophallus was chosen to describe the penis","source":1,"locator":"p. 692","quote":"the name dolichophallus has been selected which more suitably indicates the most characteristic feature."},{"text":"During mating, the thin end of the penis can tie itself in a knot inside the partner, anchoring it in place","source":1,"locator":"p. 704","quote":"The mechanical difficulty in dolichophallus is incurred by the extremely attenuate apical penis which literally ties itself into a knot while in the spermatheca of its partner thereby inextricably anchoring itself."},{"text":"Apophallation (the penis being chewed off at the end of mating) occurs in A. dolichophallus as well as A. californicus","source":2,"locator":"p. 121 (Introduction)","quote":"Apophallation is a behavior first observed in Ariolimax (Meadarion) californicus (Cooper, 1872) (Heath 1916, Leonard et al. 2002) and subsequently in Ariolimax (Meadarion) dolichophallus Mead, 1943 (Mead 1942, 1943, Harper 1988, Leonard et al. 2002) whereby the penis is sometimes chewed off at the end of copulation in these simultaneous hermaphrodites."},{"text":"Banana slugs are simultaneous hermaphrodites","source":2,"locator":"p. 121 (Introduction)","quote":"whereby the penis is sometimes chewed off at the end of copulation in these simultaneous hermaphrodites."},{"text":"Body colour is opaque butter yellow","source":1,"locator":"p. 690 (External)","quote":"External.—Ground color opaque butter yellow; mantle concolorous."},{"text":"First eyewitness account of apophallation, in the related A. californicus: the partner gnawed through the penis within minutes","source":3,"locator":"p. 23","quote":"one of the animals turned its head and commenced to gnaw upon the walls of the organ."}],"sources":[{"id":1,"label":"Mead A.R. (1943) Revision of the giant West Coast land slugs of the genus Ariolimax Moerch (Pulmonata: Arionidae). The American Midland Naturalist 30(3):675–717","doi":"10.2307/2421211","url":"https://archive.org/details/sim_american-midland-naturalist_1943-11_30_3","type":"peer-reviewed","verified":"2026-10-30, full text (Internet Archive scan of the issue, OCR checked against page images)"},{"id":2,"label":"Leonard J.L., Westfall J.A., Pearse J.S. (2007) Phally polymorphism and reproductive biology in Ariolimax (Ariolimax) buttoni (Pilsbry and Vanatta, 1896) (Stylommatophora: Arionidae). American Malacological Bulletin 23:121–135","url":"https://archive.org/details/biostor-232917","type":"peer-reviewed","verified":"2026-10-30, full text (BioStor PDF; OCR typos corrected in quote)"},{"id":3,"label":"Heath H. (1916) The conjugation of Ariolimax californicus. The Nautilus 30:22–24","url":"https://archive.org/details/biostor-130708","type":"peer-reviewed","verified":"2026-10-30, full text (BioStor PDF)"}],"imageRefs":[{"label":"Mead 1943, Plate 1, Fig. 4 (p. 714)","what":"Line drawing of the basal genital structures of A. dolichophallus showing the whole penis: thick basal portion and long looping whip-like apical portion with knobbed tip; 5 mm scale bar on the plate"},{"label":"Mead 1943, Plate 3, Fig. 16","what":"Photograph of dissected genitalia of A. dolichophallus; the penis is the long thin filament on the left"}],"artNotes":"Drawn from the dissected organ in Mead's Plate 1 Fig. 4 and laid in a loose loop, because the whip-like end is far too long to show straight without shrinking the base to nothing. The true-size length follows the centreline for the full 85 mm. Mead does not give the colour, so we used a neutral pale cream. Proportions taken off the figure are good to about ±10%. This is the relaxed, dissected penis (60–110 mm), shorter than the extended foot (150–180 mm). When Mead says it is sometimes longer than the slug he is talking about some individuals, and about something other than this typical relaxed length.","artSimplifications":["Rest of the reproductive tract and retractor muscle omitted","Internal folds of the basal wall not shown","Colour not sourced"],"plate":{"src":{"256":"plates/banana-slug/256.webp","640":"plates/banana-slug/640.webp","1600":"plates/banana-slug/1600.webp","full":"plates/banana-slug/full.webp"},"w":2074,"h":943,"pxPerMm":47.1416,"a":[43.1,150.4],"b":[1283.8,903.7],"path":[[43.1,150.4],[95.1,144.2],[169.6,135.4],[247.5,127.2],[323.2,120.9],[402.1,115.2],[481.1,109.6],[558.8,103.6],[636.7,97.7],[714.6,92],[792.3,87],[870.2,82.3],[948.1,77.4],[1025.9,72.5],[1103.8,67.5],[1181.5,62.9],[1259.4,58.6],[1337.3,54.7],[1415.1,51.2],[1495.2,47.4],[1575.2,44],[1648.6,42.4],[1713,42.7],[1770.8,44.8],[1823.7,51.2],[1873.2,62.1],[1917.8,77.3],[1955.1,97.9],[1984.3,125.1],[2006.4,157.7],[2022.3,194.2],[2032,235.4],[2035.5,280.6],[2034,325.6],[2027.7,370.5],[2016.2,415.4],[1998.9,457],[1975.2,495.1],[1945.7,529.9],[1911.4,559.2],[1871.9,581.8],[1827.5,598.9],[1780,611.7],[1729.1,620.5],[1675.1,625.1],[1619.5,626.4],[1561.6,624.8],[1502.1,620.1],[1444.3,611.7],[1388.6,599.1],[1334.5,582.6],[1283.8,565],[1236.7,545.8],[1192.9,525.2],[1152.4,506.7],[1115.1,490.2],[1081.1,475.7],[1050.3,465.8],[1021.8,460.4],[996.8,459.5],[977.2,465.8],[962.8,481.3],[953.8,504],[953.8,530.1],[965.5,559.5],[986.3,592.1],[1012.2,623.4],[1044.5,651.9],[1081.9,679],[1117.4,705.1],[1149.2,730.8],[1179.2,755.3],[1204.9,778.1],[1225,798.3],[1240.9,817],[1254.5,836.5],[1266.9,860.8],[1277,886],[1283.8,903.7],[1283.8,903.7]]},"portrait":{"src":{"256":"portraits/banana-slug/256.webp","640":"portraits/banana-slug/640.webp","1200":"portraits/banana-slug/1200.webp"},"w":2190,"h":454,"alt":"A slender banana slug, drawn side-on.","credit":"Drawn after a photo by Linda Tanner (Wikimedia Commons, CC BY 2.0)."}},{"id":"bank-card","kind":"reference-object","common":"Bank card (ISO/IEC 7810 ID-1)","scientific":"","group":"Reference objects","tags":[],"measure":"Card width (long edge), nominal ISO/IEC 7810 ID-1 dimension","state":"unknown","valueMm":85.6,"confidence":"high","fact":"ID-1 cards measure 85.60 by 53.98 mm, with corners rounded to a 3.18 mm radius. Machine-readable identity cards (ICAO 'TD1') are the same size.","marginNote":"A committee settled that corner radius to a hundredth of a millimetre, which is more care than most of us give anything.","claims":[{"text":"ID-1 nominal size 85.60 × 53.98 mm (ISO/IEC 7810:2019)","source":1,"locator":"§2.1, p. 1","quote":"The nominal dimensions shall be those specified in ISO/IEC 7810: 2019 for the ID-1 type card: 85.60 mm (3.370 in) wide by 53.98 mm (2.125 in) high"},{"text":"Corner radius 3.18 mm ± 0.30 mm","source":1,"locator":"Figure 2, p. 2 (PDF p. 10)","quote":"R 3.18 +/- 0.30 (0.125 +/- 0.012)"},{"text":"Card height 53.98 mm","source":1,"locator":"Figure 2, p. 2","quote":"53.98 +/- 0.75 (2.13 +/- 0.03)"},{"text":"TD1 documents may be 0.25–1.25 mm thick, a looser tolerance than ISO/IEC 7810 for historical reasons","source":1,"locator":"§2.4 Thickness, p. 3 (PDF p. 11)","quote":"Note.— The tolerances specified above differ from those specified in ISO/IEC 7810 for the ID-1 size card. This is for historical reasons; TD1 cards were originally produced using encapsulated pouch card methods which are incapable of achieving the permitted tolerances of ISO/IEC 7810."}],"sources":[{"id":1,"label":"ICAO (2021) Doc 9303 Machine Readable Travel Documents, Eighth Edition, Part 5: Specifications for TD1 Size Machine Readable Official Travel Documents (MROTDs). International Civil Aviation Organization, Montréal","url":"https://www.icao.int/sites/default/files/publications/DocSeries/9303_p5_cons_en.pdf","type":"standard","verified":"2026-10-30, full text (official ICAO PDF; ISO/IEC 7810 itself is paywalled and was not read)"}],"imageRefs":[{"label":"ICAO Doc 9303 Part 5 (2021), Figure 2","what":"Dimensioned outline of the ID-1/TD1 card: 85.6 × 53.98 mm, corner radius R 3.18"}],"artNotes":"This is a calibration object, so the outline is exact and the true-size length is the 85.60 mm long edge. The ±0.75 mm tolerance in the ICAO drawing belongs to TD1, which is looser than ISO 7810, so we used the nominal sizes. The face is blank on purpose.","artSimplifications":["Blank card: no chip, magnetic stripe, embossing or printing","Thickness not shown (face-on view)"],"plate":{"src":{"256":"plates/bank-card/256.webp","640":"plates/bank-card/640.webp","1600":"plates/bank-card/1600.webp","full":"plates/bank-card/full.webp"},"w":2179,"h":1400,"pxPerMm":24.7892,"a":[26,695.3],"b":[2148,695.3]}},{"id":"komodo-dragon","kind":"specimen","common":"Komodo Dragon","scientific":"Varanus komodoensis","group":"Reptiles","tags":[],"measure":"Length of ONE fully everted, preserved hemipenis (museum preparation HGD 801), base to apex, measured by us from Böhme's scaled drawing (Abb. 38). Komodo dragons have two; only one is used at a time. The plate shows the pair","state":"everted","valueMm":105,"confidence":"low","fact":"Each Komodo dragon hemipenis ends in two cups, and each cup holds a stiff rod of cartilage. Böhme regarded it as the original, symmetrical type among the large monitors.","marginNote":"If the big monitors kept a pattern book, this would be the page marked 'original'.","claims":[{"text":"Hemipenis slender, club-shaped distally; sulcus nearly straight","source":4,"locator":"p. 118","quote":"Hemipenis schlank, distal keulenartig verdickt. Sulcus fast gerade, seine innere Lippe kräftiger als die äußere, ihn fast zum Rohr schließend."},{"text":"The apex is divided into two near-circular, sometimes concave plates ('cups'), each with a protruding stiffened apical support (hemibaculum)","source":4,"locator":"pp. 118–119","quote":"Beidseitig davon ist der Apex in zwei leicht sulcalwärts geneigte, annähernd kreisförmige und manchmal konkave Platten (,,cups\" nach Branch 1982) gegliedert, aus denen je ein verfestigtes apicales Stützelement oder Hemibaculum herausragt."},{"text":"Both hemibacula are cartilaginous, stiffest at their narrow tips; the outer one is slightly larger (as described by Böhme 1988)","source":4,"locator":"p. 119","quote":"Beide Hemibacula sind knorpelig und erreichen ihre größte Festigkeit im terminalen schmalen Endabschnitt. Das (bei Sulcalansicht) äußere Hemibaculum ist etwas größer als das innere."},{"text":"Eight frills (paryphasmata) on the asulcal side, transverse proximally and oblique distally, meeting at an acute angle on the midline; lower shaft smooth (in the specimen Böhme described)","source":4,"locator":"p. 119","quote":"Asulcal finden sich acht proximal quer, distal jedoch schräg verlaufende Paryphasmen, die auf der Medianlinie spitzwinklig zusammenlaufen. Der Trunco-Pedicelbereich ist sulcal vollständig und asulcal in der proximalen Hälfte glatt."},{"text":"The drawn specimen (HGD 801) was fully everted; a second, half-size one was not","source":4,"locator":"p. 119","quote":"Das nur halb so große und nicht komplett ausgestülpte MNCN-Präparat entspricht in seinen sichtbaren Merkmalen HGD 801."},{"text":"Among the large monitors, the Komodo dragon has the original, symmetrical type of hemipenis","source":4,"locator":"p. 20 (general part, on asymmetric hemipenes)","quote":"Der zweifellos ursprüngliche Typ des symmetrisch gebauten Hemipenis wird bei den Großwaranen durch den Komodowaran (Varanus komodoensis) verkörpert (Abb. 7a'), während der ihm äußerlich ähnliche, ebenfalls südostasiatische Bindenwaran (V. salvator) stark asymmetrische Abwandlungen nicht nur der apikalen Stützelemente, sondern auch der Schaftbekleidung zeigt (Abb. 7 b')."},{"text":"Komodo dragon hemipenes contain ossifications that show on X-rays (Shea & Reddacliff 1986)","source":2,"locator":"p. 437","quote":"Shea and Reddacliff (1986) and Davis (1991) report ossifications in hemipenes for some varanid species [V. komodoensis, V. gilleni, V. varius, (Shea and Reddacliff, 1986); V. dumerili (Davis and Phillips, 1991); V. giganteus (N. Heger, personal communication); V. eremius, unpub data] can be detected in radiographs."},{"text":"Juvenile Komodo dragons have been sexed by ultrasound (Morris et al. 1998)","source":2,"locator":"p. 437","quote":"Similarly, Morris et al. (1998) and Schildger et al. (1999) report the use of ultrasound to sex juvenile V. komodoensis and adult V. gouldii and V. indicus respectively"},{"text":"In some large monitors the hemipenes cannot be everted by finger pressure, and females have partly eversible hemiclitores that can be mistaken for hemipenes","source":2,"locator":"p. 437","quote":"For some larger species (e.g., V. mertensi) hemipenes cannot be everted with pressure applied by the fingers. Reliance on eversion of hemipenes can also be a problem for the inexperienced field worker because of the existence of hemiclitores in females."},{"text":"Two captive female Komodo dragons isolated from males produced parthenogenetic offspring; one later reproduced sexually","source":1,"locator":"Abstract","quote":"Here we use genetic fingerprinting to identify parthenogenetic offspring produced by two female Komodo dragons (Varanus komodoensis) that had been kept at separate institutions and isolated from males; one of these females subsequently produced additional offspring sexually."},{"text":"Female Komodo dragons have hemiclitoral sacs where males have hemipenes","source":3,"locator":"§1 Introduction","quote":"So far, only a relationship between the arrangement of pre-cloacal scales and gender has been recognised, along with the presence of hemiclitoreal sacs in females where males have hemipenes [ 11 ]."}],"sources":[{"id":1,"label":"Watts P.C., Buley K.R., Sanderson S., Boardman W., Ciofi C., Gibson R. (2006) Parthenogenesis in Komodo dragons. Nature 444:1021–1022","doi":"10.1038/4441021a","type":"peer-reviewed","verified":"2026-10-30, abstract only (Europe PMC record, PMID 17183308)"},{"id":2,"label":"Thompson G.G. (2002) The feasibility of using body proportions in Western Australian varanids (Varanus) as a method for determining a specimen's sex. Records of the Western Australian Museum 20:437–439","url":"https://archive.org/download/biostor-241600/biostor-241600.pdf","type":"peer-reviewed","verified":"2026-10-30, full text (BioStor PDF)"},{"id":3,"label":"Czubaj N. et al. (2024) Biological significance of the Komodo dragon's tail (Varanus komodoensis, Varanidae). Animals 14(15):2142","doi":"10.3390/ani14152142","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC11311070/","type":"peer-reviewed","verified":"2026-10-30, full text (Europe PMC XML); first-author name and author list not checked"},{"id":4,"label":"Böhme W. (1988) Zur Genitalmorphologie der Sauria: Funktionelle und stammesgeschichtliche Aspekte. Bonner Zoologische Monographien 27:1–176. Zoologisches Forschungsinstitut und Museum Alexander Koenig, Bonn","url":"https://archive.org/details/bonner-zoologische-monographien-27-0001-0176","type":"monograph","verified":"2026-10-30, full text (BHL scan via archive.org PDF), pp. 118–119 and general part read"}],"imageRefs":[{"label":"Böhme 1988, Abb. 38 a–b (p. 118)","what":"Ink drawing of the fully everted hemipenis HGD 801 in sulcal (a) and asulcal (b) views with 2 cm scale bars: slender shaft, club-shaped apex with two cups and hemibacula, paryphasmata. Used for length, proportions and all features"}],"artNotes":"Traced from Böhme's Abb. 38 and laid out with the shaft horizontal and the apex at the far end. The pair is drawn side by side, both mirrored from the one organ he described. The true-size length is one hemipenis, base to apex tip. Böhme drew a preserved museum preparation from an animal of unknown size; full eversion is implied rather than stated, and the living colour is unknown, so the plate is in neutral ink.","artSimplifications":["Paryphasma ornamentation and surface stippling simplified","Second hemipenis drawn as a mirror image of the described one","Colour not sourced"],"plate":{"src":{"256":"plates/komodo-dragon/256.webp","640":"plates/komodo-dragon/640.webp","1600":"plates/komodo-dragon/1600.webp","full":"plates/komodo-dragon/full.webp"},"w":1933,"h":1375,"pxPerMm":17.1832,"a":[107.1,953.7],"b":[1911.3,953.7]},"portrait":{"src":{"256":"portraits/komodo-dragon/256.webp","640":"portraits/komodo-dragon/640.webp","1200":"portraits/komodo-dragon/1200.webp"},"w":2477,"h":975,"alt":"A Komodo dragon, drawn side-on.","credit":"Drawn after a photo by Charles J. Sharp (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"domestic-dog","kind":"specimen","common":"Domestic Dog","scientific":"Canis familiaris","group":"Mammals","tags":["baculum"],"measure":"Length of the erect pars longa glandis, penis tip to start of the bulbus glandis (tape measure, lateral side)","state":"erect","valueMm":116.5,"rangeMm":[90,150],"confidence":"high","fact":"When a dog is erect, the bulbus glandis swells to an average of 5.75 cm long. This swelling is what holds a mating pair together in the 'tie'.","marginNote":"A lock-and-key mechanism in which the key swells.","claims":[{"text":"Erect bulbus glandis 5.75 ± 0.73 cm long; 3.53 cm after detumescence","source":1,"locator":"Ch. 4.2, 'Länge des Bulbus glandis in Gruppe B', p. 51 (PDF p. 59)","quote":"Bei der im erigierten Zustand durchgeführten Messung des Bulbus glandis konnte ein Mittelwert von 5,75 cm ± 0,73 cm errechnet werden. Nach erfolgter Detumeszenz lag der Mittelwert bei 3,53 cm ± 0,60 cm."},{"text":"Erect width at the middle of the pars longa 3.31 ± 0.52 cm","source":1,"locator":"Ch. 4.3, 'Gesamtbreite des Penis in Gruppe B', p. 52 (PDF p. 60)","quote":"Der Mittelwert dieser Messung lag bei 3,31 cm ± 0,52 cm."},{"text":"Pars longa glandis shrinks by about 42% after erection subsides (11.65 to 6.76 cm)","source":1,"locator":"Ch. 4.2, p. 50 (PDF p. 58)","quote":"Nach    erfolgter   Detumeszenz   lag   der     Mittelwert   bei 6,76 cm ± 1,26 cm. Damit betrug die Längenabnahme der Pars longa glandis während der Detumeszenz im Durchschnitt 41,97 %."},{"text":"The bulbus glandis swells during coitus to produce the copulatory tie","source":3,"locator":"Results, Gross anatomy, p. 9","quote":"The body of the penis also showed a swelling named bulbuls glandis that increased during coitus for the coital tie."},{"text":"Os penis (baculum) about 13 cm in five local Iraqi dogs; 10 cm per Sisson & Grossman","source":3,"locator":"Results p. 9; Discussion p. 12","quote":"The Os – penis appeared as part of corpus cavernosum with 13 cm length in the local dog, while its length was 10 cm in the previous study (Sisson and Grossmans, 1975)."},{"text":"The bulbus glandis surrounds the proximal part of the os penis","source":1,"locator":"Ch. 2.1.1, p. 7","quote":"Der Bulbus glandis umschließt den proximalen Anteil des Os penis."},{"text":"The os penis is grooved ventrally for the urethra and tapers to a fibrous tip","source":1,"locator":"Ch. 2.1.1, p. 7","quote":"Es hat eine verdickte Basis und verjüngt sich nach distal zu einer fibrösen Spitze. An der ventralen Fläche befindet sich der Sulcus urethralis, in dem die Urethra mit dem Corpus spongiosum verläuft"},{"text":"Group B: 36 dogs, 22 breeds, 1.5–11 years, 9.1–82 kg","source":1,"locator":"Ch. 3.2.2, p. 33 (PDF p. 41)","quote":"Es waren 22 Rassen vertreten. Die Hunde waren zwischen 1,5 und 11 Jahren alt und wiesen eine Körpermasse zwischen 9,1 und 82 kg auf."}],"sources":[{"id":1,"label":"Hölscher C. (2012) Funktionelle Anatomie und Sonographie des Rüdenpenis. Dr. med. vet. dissertation, Justus-Liebig-Universität Gießen (JLUpub, urn:nbn:de:hebis:26-opus-87509). Data published as Goericke-Pesch S., Hölscher C., Failing K., Wehrend A. (2013) Theriogenology 80(1):24–33","url":"https://jlupub.ub.uni-giessen.de/handle/jlupub/12401","type":"peer-reviewed","verified":"2026-10-30, full text PDF from JLUpub (141 pp.) read; the 2013 Theriogenology paper (doi 10.1016/j.theriogenology.2013.03.005) read as abstract only"},{"id":3,"label":"Saadon A.H. (2016) Anatomical and histological study of local dog penis. Mirror of Research in Veterinary Sciences and Animals 5(3):8–14","url":"http://mrvsa.com/upload/article%202%20Anatomical%20and%20Histological%20Study%20of%20Dog%20Penis.pdf","type":"peer-reviewed","verified":"2026-10-30, full text PDF read (small sample, n = 5, unspecified breed/size, small regional journal)"}],"imageRefs":[{"label":"Hölscher 2012, Abb. 2 (after Budras 2000)","what":"Labelled lateral anatomical overview of the (non-erect) dog penis: pars longa glandis, bulbus glandis, os penis, corpus spongiosum, urethra"},{"label":"Hölscher 2012, Abb. 5","what":"Photo of the tape-measure method: pars longa glandis and bulbus glandis lengths"}],"artNotes":"The true-size length is the pars longa glandis only, from the tip to the front edge of the bulbus glandis (116.5 mm), because that is the part the study measured. The bulbus (57.5 mm) is drawn behind it, outside the measured length, and the body of the penis behind that is left out. Thicknesses are Hölscher 2012's erect vertical diameters from Table 4: 29 mm near the tip, 35 mm at mid pars longa and 44 mm at mid bulbus. The overall width of 33.1 mm was measured at mid pars longa. Breeds differ enormously (the sample ran from 9.1 to 82 kg) and the plate shows the sample mean. There is no body length for Relative mode, since a typical dog's length means little and the study reports only body mass.","artSimplifications":["Os penis drawn as a faint internal line","Penile body behind the bulbus omitted"],"plate":{"src":{"256":"plates/domestic-dog/256.webp","640":"plates/domestic-dog/640.webp","1600":"plates/domestic-dog/1600.webp","full":"plates/domestic-dog/full.webp"},"w":2413,"h":658,"pxPerMm":13.4465,"a":[818.9,328],"b":[2385.4,328]},"portrait":{"src":{"256":"portraits/domestic-dog/256.webp","640":"portraits/domestic-dog/640.webp","1200":"portraits/domestic-dog/1200.webp"},"w":1698,"h":1307,"alt":"A male German Shepherd, drawn side-on.","credit":"Drawn after a photo by gomagoti (Wikimedia Commons, CC BY-SA 2.0)."}},{"id":"bottlenose-dolphin","kind":"specimen","common":"Common bottlenose dolphin","scientific":"Tursiops truncatus","group":"Mammals","tags":[],"measure":"Penis length from the cranial point of fusion of the sheath with the shaft to the distal tip, after artificial inflation with pressurised saline to simulate erection (before formalin fixation); longest of four orientations. This is the free part beyond the sheath, not the whole organ.","state":"erect","valueMm":121,"confidence":"low","fact":"Researchers pumped saline into one excised bottlenose dolphin penis to simulate erection. It measured 12.1 cm from the sheath to the tip, with a natural bend and a distinct tip.","marginNote":"Results may differ in a live dolphin.","claims":[{"text":"12.1 cm sheath-to-tip in one saline-inflated specimen (vaginal endocast of a female was 15.0 cm)","source":1,"locator":"ESM Table S1","quote":"Common bottlenose dolphin (Tursiops truncatus) | 15.0 | 12.1"},{"text":"Erection was simulated by inflating excised penises with pressurised saline","source":1,"locator":"Abstract","quote":"Excised penises were artificially inflated to erection with pressurized saline"},{"text":"Short shaft and tip in this species","source":1,"locator":"Results, Fig. 1b","quote":"Male common bottlenose dolphin (T. truncatus) have a short penis shaft and tip"},{"text":"There is a natural bend in the penis, and a conspicuous tip distinct from the shaft","source":1,"locator":"Results / Discussion","quote":"In both harbour porpoises and common bottlenose dolphins, there is a natural bend in the penis"},{"text":"Cetacean penis is fibroelastic","source":1,"locator":"Introduction","quote":"The cetacean penis is fibroelastic; erectile tissue is filled with collagen and elastin fibres instead of the spongy tissue found in the vascular penis of most mammals"},{"text":"The tip appears to be under voluntary control in live cetaceans (authors' personal observation)","source":1,"locator":"Discussion","quote":"it is possible that the distal filamentous penis tip may be able to navigate through the remaining cranial vaginal folds, as it appears to be under voluntary control in live cetaceans (D.N.O., personal observation)."},{"text":"The method only partly inflated the tip","source":1,"locator":"Discussion","quote":"Our technique resulted in full inflation of the penis shaft, but only partial inflation of the penis tip or cone."}],"sources":[{"id":1,"label":"Orbach D.N., Kelly D.A., Solano M., Brennan P.L.R. (2017) Genital interactions during simulated copulation among marine mammals. Proc. R. Soc. B 284:20171265 (with ESM Table S1)","doi":"10.1098/rspb.2017.1265","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC5647295/","type":"peer-reviewed","verified":"2026-10-30, PMC full text plus Table S1 docx from figshare (rs.figshare.com article 5436628)"}],"imageRefs":[{"label":"Orbach et al. 2017, Fig. 1b","what":"Inflated male reproductive tract of T. truncatus, lateral view, with the penis tip (label 4), shaft (5) and retractor muscle (6), next to the female's 15.0 cm vaginal endocast for scale"},{"label":"Orbach et al. 2017, Fig. 3b","what":"CT reconstruction of the penis inside the vagina (erectile tissue in red)"}],"artNotes":"Only the free part is shown, from where the sheath fuses with the shaft out to the tip, so the plate matches the measured 12.1 cm along the bend. Traced from Fig. 1b, inflated and fixed. The tip only partly filled during inflation, and in life it may be longer or slimmer.","artSimplifications":["Sheath and retractor muscle omitted","Surface texture of the fixed specimen omitted"],"plate":{"src":{"256":"plates/bottlenose-dolphin/256.webp","640":"plates/bottlenose-dolphin/640.webp","1600":"plates/bottlenose-dolphin/1600.webp","full":"plates/bottlenose-dolphin/full.webp"},"w":1301,"h":1046,"pxPerMm":15.1345,"a":[21.8,538.3],"b":[899.5,713.7],"path":[[21.8,538.3],[92.5,517],[194,486.7],[298.9,455.1],[388.1,429],[473,405],[555.7,380.5],[637.2,353.1],[718.7,320.9],[797.9,288.2],[871.5,261.2],[939.5,240.4],[1002.8,224.3],[1059.7,215.8],[1110.2,216.7],[1156.3,226.1],[1192.2,244],[1212.2,271.9],[1215.4,313.1],[1206.2,361.5],[1188.9,409],[1164.3,453.1],[1131,497],[1091.2,541.6],[1042.8,590],[981.3,644.5],[924.6,692.1],[899.5,713.7]]},"portrait":{"src":{"256":"portraits/bottlenose-dolphin/256.webp","640":"portraits/bottlenose-dolphin/640.webp","1200":"portraits/bottlenose-dolphin/1200.webp"},"w":2390,"h":1171,"alt":"A bottlenose dolphin, drawn side-on.","credit":"Drawn after a public-domain NASA photo (Wikimedia Commons, public domain)."}},{"id":"euro-banknote","kind":"reference-object","common":"€10 banknote (Europa series)","scientific":"","group":"Reference objects","tags":[],"measure":"Banknote length (long edge), €10 second (Europa) series","state":"unknown","valueMm":127,"confidence":"high","fact":"By ECB decision, every €10 note in either the first or the Europa series measures 127 × 67 mm. Its dominant colour is red and the architecture on it Romanesque.","marginNote":"Shown blank, because the ECB has firm views on life-size copies.","claims":[{"text":"€10 is 127 × 67 mm in both the first and second series; dominant colour red; Romanesque design","source":1,"locator":"Article 1(1), table","quote":"10 127 × 67 mm 127 × 67 mm Red Romanesque"},{"text":"The second series is the Europa series and includes the €10","source":2,"locator":"'Europa series' section","quote":"The second series, also known as the Europa series, was developed to make euro banknotes more secure against counterfeiting and more durable."},{"text":"The Europa series has six denominations including €10","source":2,"locator":"'Europa series' section","quote":"Introduced gradually over several years, the Europa series consists of six denominations: €5, €10, €20, €50, €100 and €200."},{"text":"Lawful one-sided reproductions must be ≥125% or ≤75% of the note's length and width; web reproductions need a diagonal SPECIMEN and ≤72 dpi at 100% size","source":3,"locator":"Article 1 (replacing Article 2(3) of ECB/2013/10), points (a) and (f)","quote":"one-sided reproductions of a euro banknote as specified in Article 1, provided that the size of the reproduction is equal to or greater than 125 % of both the length and width, or equal to or less than 75 % of both the length and the width of the respective euro banknote"}],"sources":[{"id":1,"label":"Decision of the European Central Bank of 19 April 2013 on the denominations, specifications, reproduction, exchange and withdrawal of euro banknotes (ECB/2013/10), 2013/211/EU, OJ L 118, 30.4.2013, p. 37; Article 1 (text as adopted, via legislation.gov.uk)","url":"https://www.legislation.gov.uk/eudn/2013/10/article/1/adopted","type":"standard","verified":"2026-10-30, full text of Article 1 (UK National Archives copy of the EU text as adopted; EUR-Lex not reachable by script)"},{"id":2,"label":"European Central Bank. Banknotes (web page, euro/banknotes/current)","url":"https://www.ecb.europa.eu/euro/banknotes/current/html/index.en.html","type":"standard","verified":"2026-10-30, full page HTML"},{"id":3,"label":"Decision (EU) 2020/2090 of the European Central Bank of 11 December 2020 amending Decision ECB/2013/10 (ECB/2020/60), Article 1","url":"https://www.legislation.gov.uk/eudn/2020/2090/article/1","type":"standard","verified":"2026-10-30, full text of Article 1"}],"imageRefs":[{"label":"ECB banknotes page, €10 Europa series front thumbnail","what":"Overall outline and red tone of the €10 Europa note (78 × 40 px thumbnail; shape and colour only)"}],"artNotes":"ECB rules (ECB/2013/10, amended by ECB/2020/60) count an on-screen image of the note's design at 100% size as a reproduction, which has to carry a large diagonal SPECIMEN and be no more than 72 dpi. To keep well clear we reproduce none of the design. The plate is a blank, red-tinted rectangle of the right size, meant as a size reference. The true-size length is the long edge (127 mm).","artSimplifications":["All design, text and security features omitted (legal and style reasons): blank red-tinted rectangle"],"plate":{"src":{"256":"plates/euro-banknote/256.webp","640":"plates/euro-banknote/640.webp","1600":"plates/euro-banknote/1600.webp","full":"plates/euro-banknote/full.webp"},"w":2419,"h":1306,"pxPerMm":18.5401,"a":[31,652.5],"b":[2385.6,652.5]}},{"id":"human","kind":"specimen","common":"Human","scientific":"Homo sapiens","group":"Mammals","tags":[],"measure":"Erect length, pubo-penile junction to meatus along the dorsal surface, fat pad pushed to the bone","state":"erect","valueMm":131.2,"bodyMm":1708,"bodyMeasure":"Global mean height (stature) of 19-year-old males in 2019, population-weighted model estimate across 200 countries (NCD-RisC); stature, not head-body length","confidence":"high","fact":"In 692 men measured by clinicians, the average erect penis was 13.12 cm long.","marginNote":"The control group.","claims":[{"text":"Average erect length 13.12 cm (SD 1.66 cm), n = 692","source":1,"locator":"Abstract p.978; Table 1 p.981","quote":"erect length [n = 692, mean (SD) 13.12 (1.66) cm] … and erect circumference [n = 381, mean (SD) 11.66 (1.10) cm]"},{"text":"Average erect circumference 11.66 cm (SD 1.10 cm), n = 381","source":1,"locator":"Abstract p.978; Table 1 p.981","quote":"erect length [n = 692, mean (SD) 13.12 (1.66) cm] … and erect circumference [n = 381, mean (SD) 11.66 (1.10) cm]"},{"text":"Erect glans width is about 0.88× the erect width at the base (3.49 vs 3.95 cm, men aged 18–19)","source":2,"locator":"Abstract p.314","quote":"The mean erect width at the base (group A, 3.95 cm; group B, 3.50 cm) and the erect width of the glans (group A, 3.49 cm; group B, 3.32 cm)"},{"text":"Glans length about 2.6 cm (measurement state not stated; the same study measured penile length stretched)","source":3,"locator":"Abstract p.402","quote":"the mean glans penis length was 2.6 ± 0.4 cm (range 1.7-3.8 cm)"},{"text":"The glans is an obtuse cone whose rim (corona) overhangs a groove behind it","source":4,"locator":"pp.1248–1249","quote":"the corona glandis, overhanging a deep retroglandular sulcus"},{"text":"Global average height of 19-year-old men in 2019: 170.8 cm (95% uncertainty 170.5-171.2 cm)","source":5,"locator":"Global height data file, row Boys / 2019 / age 19","quote":"\"Boys\",2019,19,170.835994392509,170.506073043309,171.170010094107,0.171839001529576"},{"text":"At the neck, the skin of the penis folds over on itself to form the prepuce (foreskin)","source":4,"locator":"p. 1250","quote":"At the neck it leaves the surface and becomes folded upon itself to form the prepuce or foreskin."},{"text":"An adult testis is on average 4 to 5 cm long, 2.5 cm wide and 3 cm from front to back","source":4,"locator":"p. 1240","quote":"The average dimensions of the testis are from 4 to 5 cm. in length, 2.5 cm. in breadth, and 3 cm. in the antero-posterior diameter"},{"text":"A ridge (the raphe) runs down the middle of the scrotum and continues onto the underside of the penis","source":4,"locator":"p. 1237","quote":"It is divided on its surface into two lateral portions by a ridge or raphe, which is continued forward to the under surface of the penis"}],"sources":[{"id":1,"label":"Veale D., Miles S., Bramley S., Muir G., Hodsoll J. (2015) Am I normal? A systematic review and construction of nomograms for flaccid and erect penis length and circumference in up to 15 521 men. BJU International 115(6):978–986","doi":"10.1111/bju.13010","type":"peer-reviewed","verified":"2026-10-30, full PDF"},{"id":2,"label":"Schneider T., Sperling H., Lümmen G., Syllwasschy J., Rübben H. (2001) Does penile size in younger men cause problems in condom use? Urology 57(2):314–318","doi":"10.1016/S0090-4295(00)00925-0","type":"peer-reviewed","verified":"2026-10-30, abstract only (PubMed PMID 11182344; refs/schneider2001_pubmed_abstract.txt). Full text (Elsevier) paywalled; Unpaywall reports no OA copy. Abstract confirms how erection was obtained (group A, men aged 18-19: visual and manual self-stimulation; group B: intracavernous PGE1) but not the width instrument or landmarks"},{"id":3,"label":"Shalaby M.E., Almohsen A.E., El Shahid A.R., Abd Al-Sameaa M.T., Mostafa T. (2015) Penile length-somatometric parameters relationship in healthy Egyptian men. Andrologia 47(4):402–406","doi":"10.1111/and.12275","type":"peer-reviewed","verified":"2026-10-30, abstract only (PubMed PMID 24698122; refs/shalaby2015_pubmed_abstract.txt). Wiley pdfdirect (listed by Unpaywall as free) returns a Cloudflare bot challenge to non-browser clients; no repository copy found. A corrigendum exists (Andrologia 2016;48(9):986, doi 10.1111/and.12732), content not accessible. The abstract states penile length was measured stretched but does not state the state or landmarks for glans length"},{"id":4,"label":"Gray H. (1918) Anatomy of the Human Body, 20th ed. Lea & Febiger, pp. 1237–1240, 1248–1250","url":"https://archive.org/details/anatomyofhumanbo1918gray","type":"book","verified":"2026-10-30, archive.org text (testis and scrotum passages re-read 2026-10-30)"},{"id":5,"label":"NCD Risk Factor Collaboration (NCD-RisC) (2020) Height and body-mass index trajectories of school-aged children and adolescents from 1985 to 2019 in 200 countries and territories: a pooled analysis of 2181 population-based studies with 65 million participants. The Lancet 396(10261):1511-1524; and its published global data file","doi":"10.1016/S0140-6736(20)31859-6","url":"https://www.ncdrisc.org/downloads/bmi-height-2020/height/global/NCD_RisC_Lancet_2020_height_child_adolescent_global.csv","type":"peer-reviewed","verified":"2026-10-30, global CSV downloaded from ncdrisc.org (refs/ncdrisc2020_height_global.csv); paper full text read via Europe PMC (PMC7658740, refs/ncdrisc2020_fulltext.xml). The paper itself reports country values, not the global mean; the global value is from the authors' official data release. NCD-RisC 2016 eLife (adult height by birth cohort, refs/ncdrisc2016.pdf) was checked and gives no global mean"}],"imageRefs":[{"label":"Gray 1918, Figs 1154–1156","what":"Glans capping the corpora; lateral section (flaccid) for glans shape and corona"},{"label":"Gray 1918, pp. 1237–1240","what":"Scrotum with its raphe, and testis size (4–5 cm long), used to size the scrotum"},{"label":"Generated anatomical reference (hunyuan-image-v3 on Venice, seed 7011)","what":"Side-view photograph-style reference for natural form, curvature, foreskin fold and scrotum, generated for this plate and checked against Gray 1918 / Veale 2015 / Schneider 2001 (length:width within 10 %, glans shrunk to the Schneider ratio, scrotum height within 4 % of the Gray testis length). Kept locally, not published"}],"artNotes":"This plate started from a photographic reference that we generated with an image model, because drawings built from measurements alone looked like no penis anyone has seen. We traced its outline, scaled it so the dorsal length is exactly 131.2 mm, and checked it against the sources: the length-to-width ratio was within 3 % of Veale's figures, the glans was too big and we shrank it to Schneider's ratio, and the scrotum's height came out within a few millimetres of the 4 to 5 cm testis Gray describes. A second model then painted over the tracing. The human is the only specimen drawn with its scrotum, so the plate doesn't look amputated. The gentle upward curve and the position of the retracted foreskin are typical rather than measured; nobody has published clinical figures for either that we could find. How far a foreskin pulls back in erection varies a lot between men.","artSimplifications":["Skin texture is stylised","Curvature is typical, not measured","Position of the foreskin's fold is illustrative","No pubic or scrotal hair","The body around the root is left out and faded"],"plate":{"src":{"256":"plates/human/256.webp","640":"plates/human/640.webp","1600":"plates/human/1600.webp","full":"plates/human/full.webp"},"w":2283,"h":1075,"pxPerMm":14.456,"a":[472,78.1],"b":[2253.7,362.9],"path":[[472,78.1],[474.1,78.4],[476,78.9],[478.1,79.4],[480.1,79.9],[482.1,80.1],[484.1,80.6],[486.2,81],[488.1,81.4],[490.2,82.6],[492.3,83.6],[494.2,84.4],[496.3,85.3],[498.4,86.1],[500.4,86.8],[502.5,87.7],[504.5,88.4],[506.5,89.1],[508.6,90],[510.5,90.8],[512.6,91.5],[514.7,92.3],[516.7,93],[518.7,93.7],[520.7,94.5],[522.8,95.2],[524.9,96],[526.8,96.7],[528.9,97.4],[530.8,98.1],[532.9,98.8],[535,99.5],[537,100.2],[539.1,101.1],[541,101.8],[543.1,102.5],[545.2,103.2],[547.1,103.9],[549.2,104.7],[551.2,105.4],[553.2,106.1],[555.3,106.8],[557.3,107.5],[559.4,108.2],[561.3,108.8],[563.4,109.5],[565.5,110.4],[567.4,111.1],[569.5,111.8],[571.5,112.3],[573.6,113.2],[575.7,113.9],[577.6,114.6],[579.7,115.3],[581.6,116.1],[583.7,116.9],[585.8,117.6],[587.8,118.3],[589.8,119],[591.9,119.8],[593.9,120.6],[596,121.3],[597.9,121.9],[600,122.6],[602.1,123.5],[604,124.2],[606.1,125],[608.1,125.7],[610.2,126.5],[612.2,127.2],[614.2,128],[616.3,128.7],[618.2,129.4],[620.3,130.2],[622.4,130.9],[624.4,131.6],[626.4,132.3],[628.4,133],[630.5,133.7],[632.6,134.6],[634.5,135.3],[636.6,135.9],[638.5,136.6],[640.6,137.3],[642.7,137.9],[644.7,138.4],[646.8,139.1],[648.7,139.7],[650.8,140.3],[652.7,141],[654.8,141.6],[656.9,142.3],[658.9,143],[661,143.7],[662.9,144.3],[665,145],[667.1,145.7],[669,146.3],[671.1,147],[673.1,147.5],[675.1,148.1],[677.1,148.8],[679.2,149.5],[681.3,150.1],[683.2,150.8],[685.3,151.5],[687.3,152.1],[689.3,152.8],[691.3,153.5],[693.4,154.1],[695.5,154.7],[697.4,155.4],[699.5,156.1],[701.4,156.7],[703.5,157.4],[705.6,158.1],[707.6,158.7],[709.7,159.4],[711.6,160.1],[713.7,160.7],[715.6,161.2],[717.7,162.1],[719.8,162.6],[721.8,163.2],[723.8,163.9],[725.8,164.5],[727.9,165.2],[729.8,165.9],[731.9,166.5],[734,167.1],[736,167.8],[738,168.3],[740,168.9],[742.1,169.6],[744,170.2],[746.1,170.8],[748.2,171.5],[750.1,172.1],[752.2,172.8],[754.2,173.3],[756.3,173.9],[758.2,174.6],[760.3,175.2],[762.4,175.6],[764.3,176.3],[766.4,176.9],[768.4,177.5],[770.5,178],[772.4,178.6],[774.5,179.3],[776.4,179.9],[778.5,180.6],[780.6,181.2],[782.6,181.7],[784.7,182.5],[786.6,183.2],[788.7,183.7],[790.6,184.3],[792.7,185],[794.8,185.6],[796.8,186.3],[798.9,186.7],[800.8,187.3],[802.9,188],[804.8,188.4],[806.9,189.2],[808.9,189.6],[811,190.2],[812.9,190.6],[815,191.1],[817.1,191.6],[819,192],[821.1,192.4],[823.1,193],[825.2,193.4],[827.1,193.9],[829.2,194.4],[831.1,194.9],[833.2,195.4],[835.2,195.9],[837.3,196.4],[839.2,196.8],[841.3,197.4],[843.2,197.8],[845.3,198.4],[847.3,198.8],[849.4,199.4],[851.3,199.8],[853.4,200.4],[855.3,200.7],[857.4,201.3],[859.4,201.8],[861.5,202.3],[863.6,202.8],[865.5,203.3],[867.6,203.8],[869.5,204.1],[871.6,204.7],[873.6,205.1],[875.7,205.5],[877.6,206],[879.7,206.4],[881.6,207],[883.7,207.3],[885.7,207.7],[887.8,208.2],[889.7,208.7],[891.8,209.1],[893.8,209.4],[895.8,210],[897.8,210.4],[899.9,210.7],[901.8,211.1],[903.9,211.5],[905.9,211.8],[907.9,212.2],[909.9,212.7],[912,213],[913.9,213.4],[916,213.8],[918,214.1],[920.1,214.5],[922,214.9],[923.9,215.2],[926,215.7],[928,216.1],[930.1,216.4],[932,216.8],[934.1,217.2],[936.1,217.7],[938.1,218.2],[940.1,218.5],[942.2,218.9],[944.1,219.4],[946.2,219.8],[948.2,220.2],[950.2,220.6],[952.2,220.9],[954.3,221.4],[956.2,221.8],[958.3,222.1],[960.3,222.5],[962.4,222.9],[964.3,223.4],[966.4,223.8],[968.3,224.1],[970.4,224.4],[972.4,224.8],[974.5,225.2],[976.4,225.5],[978.5,226.1],[980.4,226.5],[982.5,226.8],[984.5,227.2],[986.6,227.6],[988.5,228.1],[990.6,228.5],[992.6,228.8],[994.6,229.2],[996.6,229.5],[998.7,229.8],[1000.6,230.1],[1002.6,230.2],[1004.7,230.5],[1006.6,230.8],[1008.7,231],[1010.6,231.3],[1012.7,231.5],[1014.7,231.6],[1016.6,231.8],[1018.7,231.9],[1020.7,232],[1022.7,232.2],[1024.7,232.3],[1026.6,232.5],[1028.7,232.6],[1030.7,232.8],[1032.8,232.9],[1034.7,233],[1036.8,233.2],[1038.7,233.3],[1040.7,233.5],[1042.8,233.6],[1044.7,233.8],[1046.8,233.9],[1048.8,234],[1050.7,234.2],[1052.8,234.5],[1054.8,234.8],[1056.8,234.9],[1058.8,235],[1060.7,235.2],[1062.8,235.3],[1064.8,235.6],[1066.9,235.9],[1068.8,236],[1070.9,236.3],[1072.8,236.5],[1074.8,236.6],[1076.9,236.7],[1078.8,236.9],[1080.9,237],[1082.9,237.2],[1084.8,237.3],[1086.9,237.2],[1088.8,237.2],[1090.8,237],[1092.9,236.9],[1094.8,236.9],[1096.8,236.7],[1098.9,236.5],[1100.8,236.3],[1102.8,236],[1104.8,235.9],[1106.8,235.6],[1108.7,235.5],[1110.7,235.2],[1112.8,235],[1114.7,234.8],[1116.7,234.6],[1118.8,234.3],[1120.7,234.3],[1122.7,234.3],[1124.7,234.3],[1126.7,234.5],[1128.6,234.5],[1130.7,234.5],[1132.7,234.5],[1134.6,234.5],[1136.7,234.5],[1138.7,234.5],[1140.6,234.6],[1142.7,234.8],[1144.6,234.9],[1146.7,235],[1148.7,235.2],[1150.8,235.3],[1152.7,235.5],[1154.7,235.5],[1156.8,235.5],[1158.7,235.5],[1160.6,235.5],[1162.7,235.5],[1164.7,235.5],[1166.6,235.6],[1168.7,235.6],[1170.7,235.6],[1172.8,235.6],[1174.7,235.6],[1176.6,235.5],[1178.7,235.5],[1180.7,235.3],[1182.6,235.2],[1184.7,235.2],[1186.7,234.9],[1188.6,234.8],[1190.6,234.5],[1192.7,234.2],[1194.6,234],[1196.5,233.8],[1198.5,233.6],[1200.6,233.3],[1202.5,233.2],[1204.5,232.9],[1206.6,232.8],[1208.5,232.5],[1210.5,232.3],[1212.4,232],[1214.5,231.9],[1216.4,231.6],[1218.4,231.3],[1220.5,231.3],[1222.4,231.2],[1224.4,231],[1226.5,231],[1228.4,230.9],[1230.4,230.8],[1232.4,230.8],[1234.4,230.6],[1236.3,230.3],[1238.3,230.2],[1240.4,229.9],[1242.3,229.8],[1244.3,229.5],[1246.4,229.3],[1248.3,229.1],[1250.3,228.9],[1252.2,228.9],[1254.3,228.8],[1256.2,228.6],[1258.2,228.6],[1260.3,228.5],[1262.2,228.3],[1264.2,228.2],[1266.3,227.9],[1268.2,227.8],[1270.2,227.6],[1272.2,227.5],[1274.2,227.3],[1276.1,227.1],[1278.1,226.9],[1280.2,226.6],[1282.1,226.3],[1284.1,226.1],[1286,225.8],[1288.1,225.2],[1290.1,224.8],[1292,224.4],[1294,223.9],[1295.9,223.5],[1298,223.1],[1299.9,222.8],[1301.9,222.4],[1303.8,222.1],[1305.9,221.8],[1307.9,221.5],[1309.8,221.4],[1311.8,221.1],[1313.9,220.8],[1315.8,220.4],[1317.7,220.1],[1319.7,219.8],[1321.8,219.5],[1323.7,219.2],[1325.7,219.1],[1327.8,218.8],[1329.7,218.7],[1331.7,218.4],[1333.6,218.2],[1335.7,217.9],[1337.6,217.8],[1339.6,217.5],[1341.5,217.2],[1343.6,216.8],[1345.6,216.5],[1347.5,216.2],[1349.6,216.1],[1351.6,215.8],[1353.5,215.7],[1355.5,215.4],[1357.5,215.2],[1359.5,214.9],[1361.4,214.8],[1363.4,214.4],[1365.5,214.1],[1367.4,213.8],[1369.4,213.4],[1371.3,213.1],[1373.4,212.7],[1375.4,212.5],[1377.3,212.2],[1379.3,212.1],[1381.3,211.8],[1383.3,211.7],[1385.2,211.4],[1387.3,211.2],[1389.3,211],[1391.2,210.8],[1393.2,210.4],[1395.3,210.1],[1397.2,209.8],[1399.2,209.7],[1401.2,209.4],[1403.2,209.2],[1405.1,208.8],[1407.1,208.5],[1409.2,208.1],[1411.1,207.7],[1413.1,207.3],[1415,206.8],[1417,206.3],[1418.9,205.7],[1421,205.1],[1422.9,204.4],[1424.9,203.7],[1426.8,203.1],[1428.8,202.4],[1430.7,201.7],[1432.7,201],[1434.6,200.3],[1436.7,199.4],[1438.7,198.7],[1440.6,198],[1442.6,197.4],[1444.5,196.7],[1446.5,196],[1448.4,195.3],[1450.4,194.7],[1452.4,194.1],[1454.4,193.6],[1456.3,193],[1458.3,192.4],[1460.2,191.9],[1462.2,191.4],[1464.3,191],[1466.2,190.6],[1468.2,190],[1470.1,189.7],[1472.1,189.4],[1474.2,189],[1476.1,188.7],[1478.1,188.3],[1480,188],[1482.1,187.7],[1484,187.2],[1486,186.7],[1487.9,186.3],[1489.9,185.7],[1492,185.3],[1493.9,184.7],[1495.9,184.2],[1497.8,183.6],[1499.8,182.9],[1501.7,182.3],[1503.8,181.7],[1505.7,181.2],[1507.7,180.6],[1509.6,180],[1511.6,179.6],[1513.5,179.2],[1515.6,178.6],[1517.6,178.3],[1519.5,178.2],[1521.5,177.9],[1523.6,177.9],[1525.5,177.9],[1527.6,178.2],[1529.5,178.5],[1531.6,178.9],[1533.6,179.2],[1535.7,179.6],[1537.6,180],[1539.7,180.6],[1541.6,181.2],[1543.7,181.9],[1545.7,182.5],[1547.8,183],[1549.7,183.7],[1551.8,184.3],[1553.8,184.9],[1555.8,185.3],[1557.9,185.7],[1559.9,186],[1561.8,186.2],[1563.9,186.3],[1565.9,186.4],[1567.9,186.4],[1569.9,186.4],[1571.8,186.6],[1573.9,186.7],[1575.9,186.9],[1578,187.2],[1579.9,187.4],[1582,187.9],[1583.9,188.4],[1586,189],[1588,189.7],[1590.1,190.4],[1592,190.3],[1594,190.2],[1596.1,189.9],[1598,189.4],[1599.9,189],[1601.9,188.6],[1604,188.2],[1605.9,187.7],[1607.9,187],[1609.8,186.4],[1611.8,185.9],[1613.7,185],[1615.7,184.2],[1617.6,183.2],[1619.6,181.9],[1621.5,180.6],[1623.5,179.2],[1625.4,178.3],[1627.4,177.5],[1629.3,176.9],[1631.3,176],[1633.2,175.3],[1635.3,174.5],[1637.2,173.5],[1639.2,172.5],[1641.1,171.5],[1643.1,170.6],[1645,169.8],[1647,169.2],[1648.9,168.5],[1650.9,167.8],[1652.8,167.2],[1654.8,166.6],[1656.9,166.1],[1658.8,165.6],[1660.8,165.1],[1662.7,164.6],[1664.7,164.4],[1666.7,163.9],[1668.7,163.6],[1670.6,163.4],[1672.6,163.1],[1674.7,162.9],[1676.6,162.6],[1678.6,162.4],[1680.7,162.2],[1682.6,162.2],[1684.6,162.2],[1686.6,162.1],[1688.6,162.1],[1690.5,162.1],[1692.6,162.1],[1694.6,162.1],[1696.5,162.1],[1698.6,162.2],[1700.6,162.4],[1702.6,162.5],[1704.6,162.8],[1706.5,162.9],[1708.6,163.1],[1710.6,163.5],[1712.7,163.8],[1714.6,164.1],[1716.7,164.4],[1718.6,164.6],[1720.7,164.9],[1722.7,165.4],[1724.8,165.8],[1726.7,166.4],[1728.8,166.9],[1730.8,167.4],[1732.8,167.8],[1734.8,168.3],[1736.9,168.9],[1738.8,169.3],[1740.9,169.9],[1742.9,170.5],[1744.9,171.1],[1746.9,171.6],[1749,172.2],[1751.1,172.8],[1753,173.5],[1755.1,174],[1757.1,174.6],[1759.1,175.3],[1761.1,175.8],[1763.2,176.3],[1765.3,177],[1767.2,177.6],[1769.3,178.2],[1771.2,178.8],[1773.3,179.3],[1775.3,179.9],[1777.4,180.5],[1779.3,181],[1781.4,181.6],[1783.4,182.2],[1785.4,182.7],[1787.5,183.2],[1789.5,183.6],[1791.6,184.2],[1793.5,184.6],[1795.6,185.2],[1797.5,185.6],[1799.6,186],[1801.6,186.4],[1803.7,186.9],[1805.6,187.2],[1807.7,187.6],[1809.7,188],[1811.7,188.4],[1813.7,188.7],[1815.8,189.2],[1817.7,189.6],[1819.8,189.9],[1821.8,190.2],[1823.7,190.4],[1825.8,190.9],[1827.7,191.1],[1829.8,191.4],[1831.8,191.7],[1833.9,191.9],[1835.8,192.1],[1837.9,192.4],[1839.8,192.7],[1841.8,192.9],[1843.9,193.1],[1845.8,193.3],[1847.9,193.4],[1849.9,193.6],[1852,193.7],[1853.9,194],[1855.9,194.1],[1857.9,194.3],[1859.9,194.4],[1862,194.6],[1863.9,194.7],[1865.9,194.9],[1868,195],[1869.9,195.1],[1872,195.3],[1873.9,195.3],[1875.9,195.4],[1878,195.6],[1879.9,195.9],[1882,196],[1884,196],[1885.9,196.1],[1888,196.1],[1889.9,196.3],[1892,196.4],[1894,196.6],[1895.9,196.6],[1898,196.7],[1900,196.8],[1902,197],[1904,197.1],[1905.9,197.1],[1908,197.3],[1910,197.3],[1911.9,197.3],[1914,197.4],[1916,197.6],[1918.1,197.7],[1920,197.8],[1921.9,198],[1924,198.1],[1926,198.3],[1928.1,198.3],[1930,198.4],[1932,198.6],[1934.1,198.7],[1936,198.8],[1938.1,199],[1940,199.1],[1942,199.3],[1944.1,199.4],[1946,199.6],[1948.1,199.6],[1950.1,199.7],[1952,199.8],[1954.1,200],[1956,200.1],[1958.1,200.3],[1960.1,200.4],[1962,200.6],[1964.1,200.6],[1966.1,200.6],[1968.1,200.7],[1970.1,200.8],[1972,201],[1974.1,201.1],[1976.1,201.3],[1978.2,201.3],[1980.1,201.4],[1982.1,201.6],[1984.1,201.7],[1986.1,201.7],[1988,201.8],[1990.1,202],[1992.1,202],[1994.2,202.3],[1996.1,202.4],[1998.2,202.7],[2000.2,202.7],[2002.1,202.8],[2004.2,203],[2006.1,203.1],[2008.2,203.4],[2010.2,203.5],[2012.1,203.7],[2014.2,204.1],[2016.2,204.3],[2018.2,204.5],[2020.2,204.7],[2022.3,204.8],[2024.2,205.1],[2026.2,205.4],[2028.3,205.5],[2030.2,205.8],[2032.3,206],[2034.2,206.3],[2036.3,206.5],[2038.3,206.8],[2040.4,207.1],[2042.3,207.4],[2044.3,207.7],[2046.3,208],[2048.3,208.2],[2050.4,208.5],[2052.3,208.8],[2054.4,209.1],[2056.4,209.5],[2058.5,210],[2060.4,210.2],[2062.5,210.5],[2064.4,211],[2066.5,211.4],[2068.5,211.5],[2070.6,212],[2072.5,212.4],[2074.6,212.8],[2076.5,213.1],[2078.6,213.5],[2080.6,213.9],[2082.5,214.4],[2084.6,214.7],[2086.6,215.1],[2088.7,215.5],[2090.6,215.9],[2092.7,216.4],[2094.6,216.8],[2096.7,217.4],[2098.8,217.8],[2100.8,218.4],[2102.8,218.9],[2104.8,219.4],[2106.9,219.9],[2108.8,220.5],[2110.9,221.1],[2112.9,221.6],[2115,222.2],[2116.9,222.8],[2119,223.4],[2121.1,224.1],[2123,224.6],[2125.1,225.3],[2127.1,226.1],[2129.1,226.6],[2131.1,227.3],[2133.2,228.1],[2135.3,228.8],[2137.2,229.5],[2139.3,230.2],[2141.3,230.9],[2143.3,231.8],[2145.4,232.5],[2147.4,233.3],[2149.5,234.2],[2158.4,233.9],[2159.9,235.5],[2161.6,237.2],[2163.4,238.7],[2166.6,240.3],[2169.5,241.9],[2172.7,243.4],[2175.6,245],[2178.5,246.6],[2181.2,248.1],[2183.6,249.7],[2186.2,251.3],[2188.8,253],[2191.2,254.6],[2193.6,256.1],[2195.9,257.7],[2198,259.4],[2200.4,261],[2202.5,262.5],[2204.6,264.3],[2206.4,265.8],[2208.2,267.5],[2209.9,269.1],[2211.9,270.8],[2213.7,272.4],[2215.3,274.1],[2216.8,275.7],[2218.6,277.4],[2220.2,278.9],[2221.5,280.6],[2223.1,282.3],[2224.6,283.9],[2226.1,285.6],[2227.7,287.3],[2228.8,288.9],[2230.3,290.6],[2231.6,292.2],[2232.8,293.7],[2233.6,295.5],[2234.9,297.2],[2235.9,298.9],[2237.1,300.4],[2238,302.2],[2239.2,303.9],[2240.2,305.6],[2241.4,307.3],[2242.3,309],[2243.2,310.6],[2244.2,312.3],[2245.2,314],[2245.8,315.7],[2246.5,317.4],[2247.1,319.1],[2247.7,320.8],[2248.4,322.5],[2249.1,324.4],[2249.7,326.1],[2250.3,327.8],[2251,329.5],[2251.5,331.2],[2252,332.9],[2252.7,334.6],[2253.1,336.5],[2253.4,338.2],[2253.8,339.9],[2254.1,341.6],[2254.5,343.3],[2254.7,345.2],[2254.7,346.9],[2254.8,348.6],[2254.9,350.5],[2254.9,352.2],[2255.1,353.9],[2255.1,355.7],[2254.9,357.4],[2254.7,359.3],[2254.2,361],[2253.7,362.9]]},"signatureAnimation":"participation-trophy","portrait":{"src":{"256":"portraits/human/256.webp","640":"portraits/human/640.webp","1200":"portraits/human/1200.webp"},"w":611,"h":1769,"alt":"A man in Victorian field clothes, drawn side-on with a leather satchel over his shoulder.","credit":"Drawn after an 1860s studio photo by Maull & Fox (for the clothes) (Wikimedia Commons, public domain)."}},{"id":"mallard","kind":"specimen","common":"Mallard","scientific":"Anas platyrhynchos","group":"Birds","tags":["corkscrew","spines"],"measure":"Length of the manually, fully everted, formalin-fixed phallus, measured with dental floss laid in the sulcus from base to tip","state":"everted","valueMm":132,"bodyMm":530,"bodyMeasure":"Total length, midpoint of the published 40–66 cm range for the species (all subspecies, sexes combined)","confidence":"medium","fact":"Fully everted and measured along the sperm groove, the phalluses of two mallard drakes averaged 13.2 cm. They coil anticlockwise, while the female's vagina coils clockwise.","claims":[{"text":"Mallard phallus length 13.2 cm (n = 2 males)","source":1,"locator":"Table S1, row 'Anas platyrhynchos'","quote":"Table S1. Length (cm) and elaboration of waterfowl genitalia. … Species | Sex | N | Phallus length | … Anas platyrhynchos | M | 2 | 13.2"},{"text":"Measured on manually, fully everted, formalin-fixed phalluses, with dental floss laid in the sulcus from base to tip","source":1,"locator":"p.5, Materials and Methods, Specimens","quote":"The phallus was manually everted until the entire phallus was exposed and the ostium (or distal tip) had been reached. Length measurements were taken from fully everted, formalin-fixed phalluses by using dental floss placed inside the sulcus of the phallus from the base to the tip."},{"text":"The domestic descendant, the Pekin duck, measured 15.5 cm (n = 3, farm specimens)","source":1,"locator":"Table S1, row 'Anas domesticus*'","quote":"Anas domesticus* | M | 3 | 15.5 … *Specimens from commercial farms"},{"text":"Mallards are a species with a long phallus, high levels of forced copulation, and very elaborate vaginas in females","source":1,"locator":"p.2, Figure 2 caption, panel D","quote":"(C) Long-tailed duck (Clangula hyemalis), and (D) Mallard Anas platyrhynchos two species with a long phallus and high levels of forced copulations, in which females have very elaborate vaginas (size bars = 2 cm)."},{"text":"Female waterfowl vaginas have dead-end sacs and clockwise coils that appear to exclude the counter-clockwise phallus without female cooperation","source":1,"locator":"p.1, Abstract","quote":"This variation comprises two anatomical novelties: (i) dead end sacs, and (ii) clockwise coils. These vaginal structures appear to function to exclude the intromission of the counter-clockwise spiralling male phallus without female cooperation."},{"text":"Female mallards in the study had 2 vaginal pouches and 3.6 spirals (vaginal length 13.7 cm, n = 3)","source":1,"locator":"Table S1, row 'Anas platyrhynchos' (columns Sex, N, Vaginal length, Pouches, Spirals)","quote":"Anas platyrhynchos | M | 2 | 13.2 | F | 3 | 13.7 | 2 | 3.6"},{"text":"Only about 3% of bird species have a phallus","source":1,"locator":"p.1, Introduction","quote":"Only 3% of all avian species possess a phallus, or intromittent organ [14], and these species are all members of basal lineages of extant birds [14,15]."},{"text":"Specimens were dissected after collection","source":1,"locator":"p.5, Materials and Methods, Specimens","quote":"Birds were weighed and dissected in the field as soon as they were collected, or frozen the day of collection and dissected in the laboratory."},{"text":"The duck phallus spirals counterclockwise; the female oviduct spirals clockwise (Pekin duck, the domestic mallard)","source":2,"locator":"Figure 1 caption","quote":"( a ) Male and female genitalia in a Pekin duck ( Anas sp.). The male phallus (right) spirals in a counterclockwise direction and the female oviduct (left) spirals in a clockwise direction."},{"text":"Mallard penis histology: surface covered with keratinized ridges and spines pointing backward toward the base","source":2,"locator":"§2(d) Histology and §3 Results (histology paragraph)","quote":"we injected the penis of two fresh specimens of male mallard ( Anas platyrhyncos ) with saline solution … The surface of the penis is covered with keratinized ridges and spines. The ridges run around the circumference of the penis, but vary in precise position and orientation on the outer surface of the spiral. The spines are oriented with their tips facing backward towards the base of the penis."},{"text":"At rest the penis is kept inverted inside the cloaca; it is everted by lymph, not blood","source":2,"locator":"§1 Introduction","quote":"At rest, the penis is kept inverted (i.e. outside-in) within the phallic sac ( saccus phalli ) in the ventral wall of the cloaca. Unlike other amniotes, the erectile mechanism of the avian penis is lymphatic rather than vascular ( Gerhardt 1933 )."},{"text":"The waterfowl penis is flexible when erect","source":2,"locator":"Abstract","quote":"The collagen matrix of the penis is very thin and not arranged in an axial-orthogonal array, resulting in a penis that is flexible when erect."},{"text":"In the related Muscovy duck (not mallard), eversion takes about a third of a second","source":2,"locator":"Abstract","quote":"Eversion of the 20 cm muscovy duck penis is explosive, taking an average of 0.36 s, and achieving a maximum velocity of 1.6 m s −1 ."}],"sources":[{"id":1,"label":"Brennan P.L.R., Prum R.O., McCracken K.G., Sorenson M.D., Wilson R.E., Birkhead T.R. (2007) Coevolution of male and female genital morphology in waterfowl. PLoS ONE 2(5): e418","doi":"10.1371/journal.pone.0000418","url":"https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0000418","type":"peer-reviewed","verified":"2026-10-30, full text (PLoS PDF) and Table S1 (.doc supplement; cell boundaries checked in the raw file)"},{"id":2,"label":"Brennan P.L.R., Clark C.J., Prum R.O. (2010) Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia. Proc. R. Soc. B 277:1309–1314","doi":"10.1098/rspb.2009.2139","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC2871948/","type":"peer-reviewed","verified":"2026-10-30, PMC full text"},{"id":3,"label":"Johnsgard P.A. (1978) Ducks, Geese, and Swans of the World. University of Nebraska Press. Tribe Anatini chapter (UNL DigitalCommons edition)","url":"https://digitalcommons.unl.edu/biosciducksgeeseswans/12","type":"monograph","verified":"2026-10-30, full text of the Anatini chapter PDF (via Wayback copy of the UNL DigitalCommons file)"}],"imageRefs":[{"label":"Brennan et al. 2007, PLoS ONE, Fig. 2D","what":"Mallard male phallus (bracketed, coiled, ridged, tip curled) beside the female's coiled vagina; 2 cm scale bar"},{"label":"Brennan et al. 2010, Proc R Soc B, Fig. 1a","what":"Pekin duck (domestic mallard) phallus, lateral view: anticlockwise spiral, sulcus spermaticus, tip (a. ph.); 2 cm scale bar"}],"artNotes":"Coils anticlockwise (Brennan 2010). The number and tightness of the coils follow Brennan 2007 Fig. 2D (mallard), and the side outline follows Fig. 1a (Pekin duck). The true-size length runs along the groove around the coil (13.2 cm), which is longer than the coiled organ's straight-line extent. The helix is tilted a little so it reads. We found no description of the live colour, so the plate is in monochrome ink.","artSimplifications":["Ridge and spine count simplified","Coil count illustrative (fixed specimens vary in how tightly they coil)"],"plate":{"src":{"256":"plates/mallard/256.webp","640":"plates/mallard/640.webp","1600":"plates/mallard/1600.webp","full":"plates/mallard/full.webp"},"w":2070,"h":868,"pxPerMm":39.4639,"a":[162.3,532.4],"b":[1910.9,74.2],"path":[[162.3,532.4],[164.5,526.2],[166.8,520.1],[169,514.1],[171.4,507.9],[173.8,501.9],[176.4,495.8],[178.9,489.8],[181.6,483.9],[184.3,478.1],[187,472.3],[189.8,466.6],[192.6,461],[195.4,455.4],[198.4,450],[201.4,444.6],[204.5,439.5],[207.6,434.3],[210.7,429.3],[213.9,424.6],[217.2,419.8],[220.4,415.2],[223.8,410.8],[227.2,406.5],[230.6,402.3],[234.1,398.5],[237.7,394.7],[241.2,391.1],[244.7,387.7],[248.3,384.4],[251.9,381.4],[255.6,378.5],[259.3,375.8],[263.1,373.4],[266.8,371.1],[270.6,369.1],[274.4,367.2],[278.1,365.6],[281.9,364.2],[285.8,362.9],[289.7,361.9],[293.5,361.2],[297.3,360.6],[301.2,360.2],[305,360],[308.9,360.2],[312.8,360.5],[316.6,361],[320.4,361.7],[324.3,362.6],[328.1,363.8],[331.9,365.2],[335.7,366.8],[339.5,368.6],[343.3,370.6],[347,372.8],[350.8,375.2],[354.5,377.8],[358.2,380.7],[361.8,383.7],[365.4,386.8],[369,390.3],[372.6,393.9],[376.1,397.6],[379.5,401.5],[383,405.5],[386.4,409.8],[389.7,414.1],[393,418.7],[396.3,423.4],[399.5,428.2],[402.6,433.2],[405.8,438.2],[408.9,443.4],[411.8,448.7],[414.8,454.1],[417.8,459.7],[420.6,465.3],[423.4,470.9],[426.1,476.8],[428.8,482.5],[431.5,488.5],[434,494.4],[436.5,500.4],[438.9,506.5],[441.3,512.6],[443.7,518.6],[446,524.8],[448.1,531],[450.4,537],[452.4,543.2],[454.5,549.3],[456.5,555.4],[458.3,561.5],[460.1,567.6],[462,573.4],[463.7,579.5],[465.4,585.3],[467,591.1],[468.6,596.8],[470.2,602.4],[471.6,608],[473,613.4],[474.3,618.9],[475.7,624.1],[476.8,629.2],[478.1,634.2],[479.2,639.1],[480.3,643.8],[481.3,648.4],[482.3,652.9],[483.3,657.2],[484.3,661.3],[485.1,665.4],[486,669.2],[486.8,672.8],[487.5,676.3],[488.2,679.6],[488.9,682.7],[489.6,685.6],[490.4,688.3],[490.9,690.7],[491.5,693],[492,695.2],[492.6,697.1],[493.2,698.8],[493.7,700.4],[494.3,701.5],[494.7,702.7],[495.3,703.5],[495.7,704.1],[496.3,704.5],[496.7,704.7],[497.1,704.7],[497.7,704.4],[498.1,703.9],[498.7,703.2],[499.1,702.4],[499.7,701.2],[500.1,699.9],[500.7,698.3],[501.2,696.6],[501.8,694.6],[502.4,692.5],[502.9,690],[503.6,687.4],[504.3,684.7],[504.9,681.7],[505.7,678.7],[506.5,675.3],[507.2,671.8],[508,668.1],[508.9,664.2],[509.8,660.2],[510.7,656],[511.7,651.6],[512.7,647.1],[513.8,642.4],[514.9,637.7],[516.1,632.8],[517.2,627.8],[518.5,622.6],[519.9,617.3],[521.1,611.9],[522.6,606.4],[524.1,600.8],[525.7,595.1],[527.2,589.4],[528.8,583.6],[530.5,577.7],[532.3,571.7],[534.1,565.7],[536,559.7],[537.8,553.6],[539.9,547.5],[541.9,541.5],[544,535.3],[546.1,529.1],[548.4,522.9],[550.7,516.9],[553.1,510.8],[555.5,504.7],[558,498.7],[560.5,492.7],[563.1,486.7],[565.8,480.8],[568.5,475],[571.1,469.3],[574,463.6],[576.9,458],[579.8,452.5],[582.7,447.2],[585.8,441.9],[588.9,436.8],[592,431.7],[595.2,426.7],[598.4,422],[601.6,417.4],[605,412.8],[608.4,408.5],[611.8,404.3],[615.2,400.3],[618.7,396.5],[622.3,392.7],[625.8,389.3],[629.3,386],[633,382.8],[636.7,379.8],[640.3,377.1],[644,374.5],[647.8,372.2],[651.5,370.1],[655.3,368.1],[659.1,366.3],[662.9,364.8],[666.8,363.5],[670.6,362.3],[674.4,361.5],[678.2,360.7],[682.2,360.3],[686,360],[689.8,360],[693.7,360.3],[697.6,360.7],[701.4,361.3],[705.3,362.2],[709.1,363.2],[712.9,364.5],[716.8,366.1],[720.6,367.8],[724.2,369.6],[728.1,371.8],[731.7,374.1],[735.5,376.7],[739.2,379.4],[742.9,382.3],[746.4,385.4],[750.1,388.7],[753.6,392.2],[757.2,395.7],[760.7,399.6],[764.1,403.6],[767.5,407.8],[770.9,412.1],[774.2,416.5],[777.5,421.1],[780.7,425.9],[783.8,430.7],[787.1,435.8],[790.2,440.9],[793.2,446.2],[796.1,451.5],[799.1,457.1],[802.1,462.6],[804.9,468.3],[807.6,474],[810.3,479.8],[812.9,485.7],[815.6,491.7],[818.2,497.6],[820.6,503.6],[823,509.8],[825.4,515.8],[827.6,521.9],[829.9,528.1],[832.2,534.1],[834.3,540.3],[836.2,546.5],[838.2,552.5],[840.2,558.7],[842,564.7],[843.9,570.7],[845.7,576.6],[847.4,582.5],[849.1,588.3],[850.7,594.1],[852.2,599.8],[853.6,605.4],[855,610.9],[856.4,616.3],[857.7,621.6],[859,626.8],[860.3,631.9],[861.4,636.8],[862.5,641.7],[863.6,646.3],[864.6,650.9],[865.6,655.2],[866.6,659.5],[867.5,663.5],[868.3,667.4],[869.2,671.1],[869.9,674.7],[870.7,678],[871.4,681.3],[872.1,684.3],[872.8,687],[873.4,689.6],[874,692],[874.7,694.2],[875.2,696.2],[875.8,698.1],[876.2,699.6],[876.8,700.9],[877.3,702.2],[877.8,703.1],[878.3,703.8],[878.8,704.4],[879.2,704.7],[879.7,704.7],[880.2,704.5],[880.7,704.2],[881.2,703.7],[881.6,702.8],[882.1,701.8],[882.7,700.5],[883.1,699.1],[883.7,697.5],[884.3,695.6],[884.8,693.5],[885.4,691.2],[886.1,688.7],[886.7,686],[887.4,683.1],[888.1,680.1],[888.8,676.8],[889.6,673.4],[890.3,669.8],[891.2,666.1],[892.2,662.1],[893,658],[894,653.7],[895,649.3],[896,644.7],[897.1,640],[898.3,635.1],[899.4,630.1],[900.7,625.1],[901.9,619.8],[903.3,614.4],[904.7,609],[906.2,603.4],[907.6,597.8],[909.1,592.1],[910.8,586.3],[912.5,580.5],[914.2,574.6],[916,568.6],[917.9,562.5],[919.7,556.5],[921.7,550.3],[923.7,544.3],[925.8,538.2],[927.9,532],[930.2,525.8],[932.4,519.8],[934.7,513.6],[937.1,507.6],[939.5,501.4],[942,495.6],[944.6,489.5],[947.3,483.7],[949.9,477.8],[952.6,472],[955.5,466.3],[958.3,460.7],[961.2,455.1],[964.1,449.7],[967.2,444.4],[970.1,439.2],[973.2,434],[976.5,429],[979.6,424.3],[983,419.5],[986.2,415],[989.6,410.5],[993,406.2],[996.4,402.2],[999.8,398.2],[1003.3,394.4],[1006.9,390.9],[1010.5,387.4],[1014.1,384.3],[1017.7,381.3],[1021.4,378.4],[1025.1,375.7],[1028.8,373.2],[1032.6,370.9],[1036.2,368.9],[1040.1,367.1],[1043.9,365.5],[1047.7,364],[1051.5,362.9],[1055.3,361.9],[1059.3,361],[1063.1,360.5],[1066.9,360.2],[1070.8,360],[1074.7,360.2],[1078.5,360.5],[1082.4,361],[1086.2,361.7],[1090.1,362.8],[1093.9,363.9],[1097.7,365.3],[1101.5,366.9],[1105.3,368.8],[1109,370.8],[1112.8,372.9],[1116.5,375.4],[1120.3,378.1],[1123.8,380.8],[1127.5,383.8],[1131.2,387.1],[1134.7,390.4],[1138.2,394],[1141.7,397.7],[1145.3,401.8],[1148.7,405.8],[1152.1,410.1],[1155.4,414.4],[1158.7,419],[1161.9,423.7],[1165.2,428.4],[1168.3,433.5],[1171.4,438.5],[1174.5,443.8],[1177.5,449.1],[1180.4,454.4],[1183.4,460],[1186.2,465.6],[1189.1,471.3],[1191.7,477.1],[1194.4,482.9],[1197.1,488.8],[1199.7,494.8],[1202.2,500.9],[1204.6,506.9],[1207,512.9],[1209.4,519.1],[1211.7,525.1],[1213.8,531.3],[1216,537.4],[1218,543.6],[1220.1,549.6],[1222.1,555.8],[1223.9,561.8],[1225.8,567.8],[1227.6,573.9],[1229.3,579.7],[1231,585.6],[1232.7,591.4],[1234.3,597.1],[1235.7,602.8],[1237.2,608.3],[1238.5,613.7],[1239.9,619.2],[1241.2,624.3],[1242.4,629.5],[1243.6,634.5],[1244.7,639.4],[1245.8,644.1],[1247,648.7],[1248,653.2],[1248.9,657.5],[1249.8,661.6],[1250.6,665.6],[1251.5,669.4],[1252.3,673.1],[1253,676.5],[1253.9,679.7],[1254.6,682.9],[1255.2,685.7],[1255.9,688.5],[1256.4,690.9],[1257.1,693.2],[1257.7,695.3],[1258.3,697.2],[1258.8,698.9],[1259.3,700.4],[1259.8,701.6],[1260.2,702.7],[1260.8,703.5],[1261.2,704.1],[1261.8,704.5],[1262.2,704.7],[1262.8,704.7],[1263.2,704.4],[1263.6,703.9],[1264.2,703.2],[1264.6,702.2],[1265.2,701.1],[1265.8,699.8],[1266.2,698.2],[1266.7,696.5],[1267.3,694.5],[1267.9,692.3],[1268.6,689.9],[1269.1,687.3],[1269.8,684.6],[1270.6,681.6],[1271.3,678.4],[1272,675.1],[1272.8,671.5],[1273.7,667.8],[1274.5,663.9],[1275.4,659.9],[1276.3,655.8],[1277.3,651.3],[1278.3,646.9],[1279.3,642.3],[1280.4,637.4],[1281.7,632.5],[1282.8,627.4],[1284.1,622.2],[1285.4,617],[1286.8,611.6],[1288.2,606.1],[1289.6,600.5],[1291.2,594.8],[1292.7,589.1],[1294.4,583.2],[1296.1,577.3],[1298,571.4],[1299.7,565.4],[1301.6,559.4],[1303.5,553.2],[1305.6,547.2],[1307.6,541],[1309.7,534.9],[1311.8,528.8],[1314.1,522.7],[1316.3,516.5],[1318.7,510.5],[1321.1,504.3],[1323.7,498.3],[1326.2,492.3],[1328.7,486.4],[1331.4,480.5],[1334.1,474.6],[1336.9,468.9],[1339.6,463.3],[1342.6,457.7],[1345.6,452.2],[1348.5,446.8],[1351.5,441.6],[1354.6,436.5],[1357.7,431.4],[1360.9,426.4],[1364.2,421.7],[1367.4,417.1],[1370.7,412.5],[1374.1,408.2],[1377.5,404.1],[1381,400],[1384.4,396.2],[1387.9,392.6],[1391.6,389],[1395.1,385.7],[1398.8,382.5],[1402.5,379.7],[1406.1,377],[1409.8,374.4],[1413.5,372.1],[1417.3,369.9],[1421.1,367.9],[1424.8,366.2],[1428.6,364.8],[1432.6,363.3],[1436.4,362.3],[1440.2,361.5],[1444,360.7],[1447.8,360.3],[1451.8,360],[1455.6,360],[1459.4,360.3],[1463.3,360.7],[1467.2,361.3],[1471,362.2],[1474.8,363.3],[1478.6,364.6],[1482.4,366.1],[1486.2,367.8],[1490,369.8],[1493.9,371.9],[1497.5,374.2],[1501.2,376.8],[1504.9,379.5],[1508.5,382.4],[1512.2,385.6],[1515.7,388.9],[1519.4,392.3],[1522.9,396],[1526.3,399.9],[1529.9,403.8],[1533.3,408.1],[1536.6,412.4],[1539.9,416.8],[1543.1,421.4],[1546.4,426.1],[1549.6,431],[1552.7,436.2],[1555.9,441.2],[1558.8,446.5],[1561.9,452],[1564.8,457.4],[1567.7,463],[1570.5,468.6],[1573.2,474.3],[1576.1,480.2],[1578.6,486.1],[1581.3,492],[1583.8,498],[1586.2,504],[1588.6,510],[1591,516.2],[1593.3,522.2],[1595.5,528.4],[1597.8,534.6],[1599.9,540.7],[1601.9,546.8],[1603.9,552.9],[1605.9,558.9],[1607.7,565],[1609.5,571],[1611.4,577],[1613.1,582.9],[1614.6,588.6],[1616.3,594.5],[1617.7,600.1],[1619.3,605.7],[1620.7,611.3],[1622.1,616.6],[1623.4,621.9],[1624.6,627.1],[1625.8,632.2],[1627,637.1],[1628.2,642],[1629.2,646.6],[1630.1,651.2],[1631.1,655.5],[1632.1,659.8],[1633,663.8],[1633.8,667.7],[1634.7,671.4],[1635.5,674.8],[1636.2,678.3],[1636.9,681.4],[1637.6,684.4],[1638.3,687.2],[1638.9,689.7],[1639.6,692.2],[1640.2,694.3],[1640.7,696.3],[1641.3,698.2],[1641.9,699.6],[1642.3,701.1],[1642.9,702.2],[1643.3,703.1],[1643.8,703.8],[1644.3,704.4],[1644.8,704.7],[1645.3,704.7],[1645.7,704.5],[1646.2,704.1],[1646.7,703.5],[1647.2,702.8],[1647.7,701.6],[1648.2,700.5],[1648.8,699.1],[1649.2,697.3],[1649.8,695.5],[1650.5,693.3],[1651.1,691],[1651.6,688.6],[1652.3,685.9],[1653,683],[1653.7,680],[1654.4,676.7],[1655.1,673.2],[1656,669.7],[1656.8,665.8],[1657.7,661.9],[1658.7,657.8],[1659.5,653.5],[1660.5,649],[1661.6,644.4],[1662.8,639.7],[1663.9,634.8],[1665,629.8],[1666.3,624.6],[1667.6,619.5],[1668.8,614.2],[1670.3,608.7],[1671.8,603.1],[1673.2,597.5],[1674.8,591.8],[1676.5,585.9],[1678,580],[1679.9,574.1],[1681.6,568.3],[1683.4,562.2],[1685.4,556.1],[1687.3,550.1],[1689.3,543.9],[1691.4,537.7],[1693.6,531.7],[1695.8,525.5],[1698.1,519.4],[1700.3,513.3],[1702.7,507.2],[1705.3,501.2],[1707.7,495.1],[1710.2,489.1],[1712.9,483.2],[1715.6,477.3],[1718.3,471.6],[1721.1,465.9],[1723.9,460.3],[1726.9,454.8],[1729.9,449.4],[1732.8,444.1],[1735.9,438.8],[1739,433.7],[1742.2,428.7],[1745.4,424],[1748.6,419.3],[1751.9,414.7],[1755.3,410.2],[1758.7,406.1],[1762.1,401.9],[1765.6,398],[1769.1,394.3],[1772.7,390.7],[1776.2,387.3],[1779.9,384.1],[1783.4,381],[1787.1,378.2],[1790.9,375.5],[1794.6,373.1],[1798.2,370.9],[1802,368.8],[1805.8,367.1],[1809.7,365.3],[1813.5,364],[1817.3,362.8],[1821.1,361.7],[1824.9,361],[1828.9,360.5],[1832.7,360.2],[1836.5,360],[1852.3,359.2],[1867.9,356.6],[1883.1,352.4],[1897.8,346.5],[1911.8,339.2],[1925.1,330.5],[1937.2,320.4],[1948.4,309],[1958.2,296.5],[1966.9,283],[1973.9,268.8],[1979.6,253.8],[1983.5,238.3],[1985.9,222.5],[1986.8,206.4],[1985.9,190.5],[1983.4,174.6],[1979.1,159.2],[1973.5,144.2],[1966.3,130],[1957.7,116.7],[1947.7,104.2],[1936.5,92.8],[1924.2,82.8],[1910.9,74.2],[1910.9,74.2]]},"portrait":{"src":{"256":"portraits/mallard/256.webp","640":"portraits/mallard/640.webp","1200":"portraits/mallard/1200.webp"},"w":1613,"h":1343,"alt":"A mallard drake, drawn side-on.","credit":"Drawn after a photo by Commonists (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"chimpanzee","kind":"specimen","common":"Chimpanzee","scientific":"Pan troglodytes","group":"Mammals","tags":["baculum"],"measure":"Penile length during full erection (landmarks not stated in the abstract)","state":"erect","valueMm":144,"rangeMm":[100,180],"bodyMm":865,"bodyMeasure":"Adult male head-body length, midpoint of the stated range 77-96 cm (species-wide, all subspecies; not the same animals as the penis sample)","confidence":"medium","fact":"Eleven adult male chimpanzees, measured at full erection, averaged 14.4 cm. The usual '8 cm' goes back to a round number in a 1981 essay, with no sample behind it.","marginNote":"Short's figure was short.","claims":[{"text":"Erect penile length in 11 adult males: mean 14.4 cm (SD 2.02), range 10.0-18.0 cm","source":1,"locator":"Abstract, p. 267","quote":"In 11 adult males, penile length during full erection ranged from 10.0-18.0 cm (mean +/- SD = 14.4 +/- 2.02)."},{"text":"The popular '8 cm' chimpanzee figure traces to R. V. Short's 1981 review essay, which gives a round figure with no sample size or method","source":2,"locator":"Ch. 13 (pp. 319-341), section comparing genitalia of the great apes; exact page not recoverable from the full-text search","quote":"The erect penis is also very large, being 8 cm in length, and its pink color makes it particularly conspicuous."},{"text":"The penis is long and tapering, with no pronounced glans; the lips of the vertical urethral opening are thickened","source":5,"locator":"Ch. XI, Section C 'The Male Generative Organs', p. 270","quote":"The penis in that Ape is long and tapering. No pronounced glans is present, but the lips of the vertical meatus urinarius are thickened."},{"text":"The erect penis is extremely slender and blood-red; the glans is only a little thicker than the shaft and is marked by a slight curve in erection","source":6,"locator":"Troisième mémoire, pp. 209-210; Pl. XVI figs IX-X","quote":"Cette verge est extrêmement grêle, d’un rouge de sang, et singulièrement petite pour son diamètre, quoique assez longue dans l'érection. … Le gland est un peu plus gros que la partie de la verge dont il est la continuation. Son origine semble marquée par une légère courbure dans l'érection."},{"text":"When females are maximally swollen, vaginal depth averages 16.9 cm; studies with an artificial phallus suggest the filiform tip can contact the cervix","source":1,"locator":"Abstract, p. 267","quote":"when the sexual skin was maximally swollen, vaginal depth increased by up to 52% in some cases and ranged from 15.2-20.1 cm (mean +/- SD = 16.9 +/- 1.68). … Direct observations under fluoroscopy using an artificial \"penis\" loaded with radio-opaque medium showed that the filiform tip can make contact with the os cervix."},{"text":"The elongated, filiform penis may have evolved by sexual selection to negotiate the long vagina of the swollen female and to penetrate copulatory plugs","source":1,"locator":"Abstract, p. 267","quote":"Evolution of the male's elongated, filiform penis may therefore be the result of sexual selection, to negotiate the long vagina of the female and to penetrate copulatory plugs deposited during previous copulations."},{"text":"Chimpanzees have a small penis bone (baculum) of 6.0-7.8 mm","source":7,"locator":"Ch. 9, section 'The evolution of the baculum' (near Figs 9.8-9.9); page not recoverable from the full-text search","quote":"a longer baculum (14.6-15.0mm) than the gorilla (12.5 mm), chimpanzee (6.0—7.8 mm), or bonobo (8.6mm)"}],"sources":[{"id":1,"label":"Dixson A.F., Mundy N.I. (1994) Sexual behavior, sexual swelling, and penile evolution in chimpanzees (Pan troglodytes). Archives of Sexual Behavior 23(3):267-280","doi":"10.1007/BF01541563","type":"peer-reviewed","verified":"2026-10-30, abstract only (PubMed PMID 8024440); full text paywalled (Springer), not in Unpaywall"},{"id":2,"label":"Short R.V. (1981) Sexual selection in man and the great apes. In: Graham C.E. (ed.) Reproductive Biology of the Great Apes: Comparative and Biomedical Perspectives. Academic Press, New York, Ch. 13, pp. 319-341","doi":"10.1016/B978-0-12-295020-9.50019-4","url":"https://archive.org/details/reproductivebiol0000unse_h5d9","type":"book","verified":"2026-10-30, verbatim sentence fragments recovered via archive.org full-text search of the scanned book (lending-only item; page images not viewable); exact page number not available. Snippets saved in refs/short1981_fulltext_snippets.txt"},{"id":4,"label":"Mittermeier R.A., Rylands A.B., Wilson D.E. (eds) (2013) Handbook of the Mammals of the World. Vol. 3, Primates. Lynx Edicions, Barcelona. Family Hominidae, pp. 792-854 (Pan troglodytes account pp. 852-853)","url":"https://tb.plazi.org/GgServer/xhtml/03FA878540009F63FF35F750F5DBB688","type":"monograph","verified":"2026-10-30, full species-account text via Plazi TreatmentBank (refs/plazi_pan_troglodytes.html)"},{"id":5,"label":"Sonntag C.F. (1924) The Morphology and Evolution of the Apes and Man. John Bale, Sons & Danielsson, London, pp. 270-271","url":"https://archive.org/details/in.ernet.dli.2015.175221","type":"book","verified":"2026-10-30, archive.org OCR full text (refs/sonntag1924_pp270-271.txt)"},{"id":6,"label":"Duvernoy G.L. (1855-1856) Des caractères anatomiques des grands singes pseudo-anthropomorphes. Archives du Muséum d'Histoire Naturelle (Paris) 8:1-248, pls I-XVI (penis pp. 208-210, 227; Pl. XVI figs IX-X)","url":"https://archive.org/details/archivesdumusu08muse","type":"monograph","verified":"2026-10-30, full scanned volume (archive.org PDF; text and plate read). Text extract in refs/duvernoy1855_pp208-210_penis.txt"},{"id":7,"label":"Dixson A.F. (1998) Primate Sexuality: Comparative Studies of the Prosimians, Monkeys, Apes, and Human Beings. Oxford University Press","url":"https://archive.org/details/primatesexuality0000dixs","type":"monograph","verified":"2026-10-30, verbatim fragments via archive.org full-text search only (lending item; pages not viewable; page numbers unknown). refs/dixson1998_fulltext_snippets.txt"}],"imageRefs":[{"label":"Duvernoy 1855-56, Archives du Muséum 8, Pl. XVI figs IX-X","what":"Lateral view of the erect penis of a living young chimpanzee (fig. IX, drawn 'natural size'), with the short sheath (f) covering the base; fig. X partly retracted. Colour lithograph showing the blood-red colour, slender shaft, small knob-like glans (g) and slight curve near the tip"},{"label":"Duvernoy 1855-56, Pl. XVI (whole plate, with caption)","what":"Full plate for context; caption 'F. IX et X. Verge de chimpanzé, d'après le vivant'"}],"artNotes":"Outline and curve traced from Duvernoy Pl. XVI fig. IX and scaled so the full visible length, from glans tip to the base of the sheath, equals 14.4 cm. The abstract does not say where the study put its tape, so those endpoints are our assumption. Fig. IX is a young male and an adult may be proportioned differently, but we found no side view of an adult.","artSimplifications":["Proportions from a juvenile male drawn in 1855","Sheath (prepuce) drawn as a smooth sleeve","Surface texture omitted"],"plate":{"src":{"256":"plates/chimpanzee/256.webp","640":"plates/chimpanzee/640.webp","1600":"plates/chimpanzee/1600.webp","full":"plates/chimpanzee/full.webp"},"w":2413,"h":739,"pxPerMm":16.1664,"a":[164.6,437.6],"b":[2375,437.6],"path":[[164.6,437.6],[292.6,411.2],[318.9,404.2],[344.7,397.2],[399.7,383.8],[449.6,370.3],[499.3,357.3],[548.7,345.2],[597.9,333.3],[647.1,321.4],[696.6,309.4],[745.8,297.2],[795.3,285],[844.4,273.5],[893.4,262.1],[942.1,251.6],[991,241],[1039.7,230.5],[1088.6,219.7],[1137.3,209.2],[1186.3,198],[1235.2,186.9],[1283.9,176.4],[1331.5,169],[1378.5,162.9],[1424.7,158.9],[1470.4,156.4],[1515.3,155.5],[1559.8,155.9],[1604.2,156.8],[1648.8,156.8],[1692.9,158.3],[1736.7,160.6],[1780,163.9],[1822.6,169],[1865,174.7],[1906.9,182],[1948,191.2],[1988.7,201.5],[2028.8,213.1],[2068.8,225.4],[2108.5,238.2],[2144.9,251.2],[2176.9,264],[2204.8,275.7],[2228.7,286.5],[2248.6,296.1],[2264.1,305.6],[2275,315.3],[2284.7,324.6],[2294.4,334.5],[2303.5,345.4],[2311.8,358.7],[2324.3,375.6],[2329.1,383.1],[2334.4,390.2],[2375,437.6]]},"portrait":{"src":{"256":"portraits/chimpanzee/256.webp","640":"portraits/chimpanzee/640.webp","1200":"portraits/chimpanzee/1200.webp"},"w":1452,"h":1105,"alt":"An adult male chimpanzee, drawn side-on on his knuckles.","credit":"Drawn after a photo by Giles Laurent (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"smartphone","kind":"reference-object","common":"Smartphone (iPhone 17)","scientific":"","group":"Reference objects","tags":[],"measure":"Device height (long edge), Apple iPhone 17 (one specific model)","state":"unknown","valueMm":149.6,"confidence":"high","fact":"Taking one current phone as the example, the iPhone 17 is 149.6 mm tall, 71.5 mm wide and 7.95 mm thick, with a screen 15.9 cm on the diagonal.","marginNote":"Other phones are available, as a BBC presenter would hasten to add.","claims":[{"text":"149.6 mm tall, 71.5 mm wide and 7.95 mm thick; weighs 177 g","source":1,"locator":"Tech Specs, Size and Weight","quote":"Width: 71.5 mm (2.81 inches) Height: 149.6 mm (5.89 inches) Depth: 7.95 mm (0.31 inches) Weight: 177 grams (6.24 ounces)"},{"text":"Screen 15.9 cm on the diagonal, with rounded corners","source":1,"locator":"Tech Specs, Display and footnote","quote":"The iPhone 17 display has rounded corners that follow a beautiful curved design, and these corners are within a standard rectangle. When measured as a standard rectangular shape, the screen is 6.27 inches diagonally (actual viewable area is less)."},{"text":"Size varies slightly by configuration and manufacturing","source":1,"locator":"Footnote 2","quote":"Size and weight vary by configuration and manufacturing process."}],"sources":[{"id":1,"label":"Apple Inc. iPhone 17 – Technical Specifications (Apple UK web page)","url":"https://www.apple.com/uk/iphone-17/specs/","type":"other","verified":"2026-10-30, full page HTML (UK page; US page gives identical mm values)"}],"imageRefs":[{"label":"Apple iPhone 17 specs page share image","what":"Front and back views of the iPhone 17 line-up: outline, corner rounding, front screen with pill cut-out"}],"artNotes":"One particular model: the iPhone 17 as sold in Europe, with dimensions from Apple's UK specification page. The true-size length is the height, top edge to bottom edge (149.6 mm). No logo or screen content.","artSimplifications":["Screen off and blank","Side buttons omitted in face-on view","No logo"],"plate":{"src":{"256":"plates/smartphone/256.webp","640":"plates/smartphone/640.webp","1600":"plates/smartphone/1600.webp","full":"plates/smartphone/full.webp"},"w":704,"h":1365,"pxPerMm":8.8809,"a":[337,1345.6],"b":[337,17]}},{"id":"adult-hand","kind":"reference-object","common":"Adult man's hand","scientific":"","group":"Reference objects","tags":[],"measure":"Hand length, stylion (wrist) to tip of the middle finger, right hand, adult men (US Army, ANSUR II 2012)","state":"unknown","valueMm":193.3,"rangeMm":[164,239],"confidence":"high","fact":"Measured from the wrist crease to the tip of the middle finger, the average hand in the US Army's 2012 survey was 19.3 cm for men and 18.1 cm for women.","marginNote":"Please return to the US Army after use.","claims":[{"text":"Hand length = stylion (wrist) to middle fingertip, measured with a sliding caliper, fingers together, thumb abducted","source":1,"locator":"(44) Hand Length, p. 131","quote":"The length of the right hand between the stylion landmark on the wrist and the tip of the middle finger is measured with a Poech sliding caliper. The participant places the palm on a table with the fingers together and the thumb abducted."},{"text":"Men: mean 19.33 cm (n = 4082)","source":1,"locator":"p. 132","quote":"19.33 MEAN 7.61"},{"text":"Women: mean 18.11 cm, SD 1.01 cm (n = 1986)","source":1,"locator":"p. 132","quote":"18.11 MEAN 7.13 … 1.01 STANDARD DEVIATION 0.40 … NUMBER OF PARTICIPANTS 1986"},{"text":"Hand breadth (metacarpale II–V): men mean 8.83 cm, women 7.82 cm","source":1,"locator":"(42) Hand Breadth, p. 128","quote":"7.82 MEAN 3.08 8.83 MEAN 3.47"},{"text":"Palm length (middle-finger base crease to wrist): men mean 11.65 cm, women 10.87 cm","source":1,"locator":"(65) Palm Length, p. 174","quote":"10.87 MEAN 4.28 11.65 MEAN 4.59"}],"sources":[{"id":1,"label":"Gordon C.C., Blackwell C.L., Bradtmiller B., Parham J.L., Barrientos P., Paquette S.P., Corner B.D., Carson J.M., Venezia J.C., Rockwell B.M., Mucher M., Kristensen S. (2014) 2012 Anthropometric Survey of U.S. Army Personnel: Methods and Summary Statistics. Technical Report NATICK/TR-15/007, U.S. Army Natick Soldier RD&E Center (DTIC ADA611869)","url":"https://apps.dtic.mil/sti/pdfs/ADA611869.pdf","type":"other","verified":"2026-10-30, full text (DTIC PDF via Wayback Machine snapshot 20251127)"}],"imageRefs":[{"label":"Gordon et al. 2014, (44) Hand Length, p. 131 photo and diagram","what":"Right hand palm-down, fingers together, thumb abducted; wrist (stylion) to middle-fingertip measurement line"}],"artNotes":"Sized to the men's mean, from the wrist crease (stylion) to the tip of the middle finger; a woman's hand would be 181.1 mm. We traced the ANSUR II hand diagram and widened it by 1.144, easing to 1.06 at the fingertips, so the breadth comes out at the measured 88.3 mm. The fingernails are our guess.","artSimplifications":["Nails, creases and skin texture simplified","Single average-proportion hand; no sex or ancestry implied beyond the stated dataset"],"plate":{"src":{"256":"plates/adult-hand/256.webp","640":"plates/adult-hand/640.webp","1600":"plates/adult-hand/1600.webp","full":"plates/adult-hand/full.webp"},"w":2243,"h":1333,"pxPerMm":10.0093,"a":[282.8,783.1],"b":[2217.5,783.1]}},{"id":"banana","kind":"reference-object","common":"Banana (Cavendish)","scientific":"","group":"Reference objects","tags":[],"measure":"External (convex-face) length of the median outer-row finger, apex to attachment on the crown cushion, tape-measured; mean at 90–108 days after flowering (harvest), cv. 'Poyo' (Cavendish group), Côte d'Ivoire","state":"unknown","valueMm":220,"confidence":"medium","fact":"Under EU marketing rules a banana is measured along its outer curve, from the blossom end to where the stalk joins the crown, and must be at least 14 cm long.","marginNote":"The EU got here first with a tape measure.","claims":[{"text":"EU standard: length measured along the convex face, blossom end to where the peduncle joins the crown","source":2,"locator":"Annex I, III. Sizing","quote":"the length of the fruit expressed in centimetres and measured along the convex face, from the blossom end to the point where the peduncle joins the crown"},{"text":"EU minimum length 14 cm, minimum grade (thickness) 27 mm","source":2,"locator":"Annex I, III. Sizing","quote":"The minimum length permitted is 14 cm and the minimum grade permitted is 27 mm."},{"text":"Study plantation was cultivar 'Poyo', Cavendish group; 24 plants in 6 series of 4","source":1,"locator":"p. 322, Conditions de réalisation de l'étude","quote":"C'est une bananeraie de haute productivité en cultivar 'Poyo' groupe Cavendish."},{"text":"Length measured on the median finger along the outside with a tape","source":1,"locator":"p. 323","quote":"longueur externe du doigt médian de l'apex jusqu'au point d'attache sur le coussinet, mesurée avec un mètre ruban"},{"text":"Mean grade (diameter) at harvest 30.5–32.2 mm across the six series","source":1,"locator":"p. 324, table 'Grade à 108 jours'","quote":"Numéro série Grade à 108 jours I 30,5 II 31,7 III 31,1 IV 31,4 V 31,8 VI 32,2"},{"text":"Fingers get shorter from the first (oldest) hand to the last","source":1,"locator":"p. 327","quote":"D'une façon générale la longueur des fruits médians décroît avec le numéro d'ordre de la main."},{"text":"28 Cavendish cultivars: first-hand fingers 20–22 cm long","source":3,"locator":"English abstract","quote":"Finger length of first hand was between 20 and 22 cm whereas finger diameter was bigger than normal standard (around 40 mm)."}],"sources":[{"id":1,"label":"Lassoudière A., Maubert P. (1971) Évolution des dimensions des bananes entre l'émission de l'inflorescence et la récolte du régime. Fruits 26(5):321–331","url":"https://revues.cirad.fr/index.php/fruits/article/download/33801/33065/36330","type":"peer-reviewed","verified":"2026-10-30, full text (CIRAD open archive PDF, French)"},{"id":2,"label":"Commission Implementing Regulation (EU) No 1333/2011 of 19 December 2011 laying down marketing standards for bananas, Annex I (as retained in UK law, legislation.gov.uk)","url":"https://www.legislation.gov.uk/eur/2011/1333/annex/I","type":"standard","verified":"2026-10-30, full text of Annex I (UK-retained version; sizing text read; EUR-Lex not reachable by script)"},{"id":3,"label":"Evaluation of fruit characteristics of twenty-eight Cavendish subgroup banana cultivars (Musa spp., AAA Group). Journal of South China Agricultural University 25(4):6–11 (2004)","doi":"10.7671/j.issn.1001-411X.2004.04.002","url":"https://journal.scau.edu.cn/en/article/doi/10.7671/j.issn.1001-411X.2004.04.002","type":"peer-reviewed","verified":"2026-10-30, abstract only (English abstract is machine-translated per the journal site)"},{"id":4,"label":"Soltani M., Alimardani R., Omid M. (2010) A new mathematical modeling of banana fruit and comparison with actual values of dimensional properties. Modern Applied Science 4(8):104–113","url":"https://ccsenet.org/journal/index.php/mas/article/view/6157","type":"peer-reviewed","verified":"2026-10-30, full text (lengths are not tabulated in this paper)"},{"id":5,"label":"Tak M.K., Attar S.K., Tak M. Studies of banana cv. Grand Naine in the respect of correlation with growth and yield parameters. International Journal of Tropical Agriculture","url":"https://serialsjournals.com/abstract/98782_57.pdf","type":"peer-reviewed","verified":"2026-10-30, results table read"},{"id":6,"label":"Evan-Amos (2012) \"Banana-Single.jpg\", photograph of a supermarket Cavendish banana. Wikimedia Commons, CC BY-SA 3.0","url":"https://commons.wikimedia.org/wiki/File:Banana-Single.jpg","type":"other","verified":"2026-10-30, image and licence read on Commons (description: \"A common Cavendish type, bought from a supermarket in North America.\")"}],"imageRefs":[{"label":"Evan-Amos 2012, \"Banana-Single.jpg\" (Wikimedia Commons, CC BY-SA 3.0)","what":"Real photograph of one ripe Cavendish. Checked against: stalk about 0.28 of the fruit's width at its narrowest and 0.37 at the flared cut, 0.89 fruit widths from the end of the cut to where the neck widens; a ridge along the side; fibrous brown cut face; small dark blossom tip"},{"label":"Generated photographic reference (Venice, nano-banana-pro)","what":"Side view of a single ripe Cavendish on a plain background, made for tracing (PLAN 7.2a). Outline traced into reference-trace.json; also passed to the renderer for surface detail"},{"label":"Soltani et al. 2010, Figure 2 (p. 110)","what":"Schematic of a Cavendish banana showing the outer (convex) and inner length, the convention the 220 mm follows"},{"label":"Tak et al., results table (pedicel length and width)","what":"Stalk length 2.25 cm and width 1.62 cm, cv. Grand Naine. Used as a check on the stalk"}],"artNotes":"Traced from a photographic reference of an ordinary ripe Cavendish, then checked against a real supermarket banana photographed for Wikimedia Commons. It rests on its curved underside, which is also the side the 220 mm runs along, from the blossom tip round to the far end of the stalk. That is how banana standards measure it. The reference banana was a little plump, so the body has been slimmed to the 31.5 mm diameter measured in the same study as the length. Its stalk was also a few millimetres longer than the real photo's, and has been shortened to match. The study measured green bananas at export. We have painted it ripe because a green one looks like a courgette.","artSimplifications":["Outline traced from a generated photographic reference, checked against a real photograph","Fruit body slimmed to the sourced 31.5 mm diameter; stalk shortened slightly to match the real photograph","Colour (ripe yellow) from photographs; the measured fruit was green","Only the two ridges visible from the side are drawn; surface flecks simplified"],"plate":{"src":{"256":"plates/banana/256.webp","640":"plates/banana/640.webp","1600":"plates/banana/1600.webp","full":"plates/banana/full.webp"},"w":2411,"h":1031,"pxPerMm":13.3968,"a":[60.3,71],"b":[2378.2,503.3],"path":[[60.3,71],[58.1,74.2],[55.4,78.2],[52.9,82.5],[50.4,87.2],[45.9,95.4],[41.7,104.5],[38,114.5],[34.9,125.1],[32.8,136.4],[32,147.7],[32.4,159.2],[34.2,170.8],[37.2,182.1],[41.1,193.5],[46,204.6],[51.5,215.7],[57.6,226.5],[64.2,237.1],[71.2,247.4],[78.7,257.3],[86.4,267],[94.5,276.4],[103,285.3],[111.9,294],[121,302.4],[130.2,310.6],[139.6,318.8],[149,326.9],[158.4,335.1],[167.5,343.6],[176.5,352.3],[185.1,361.1],[193.4,370.4],[201.5,380],[209.4,389.8],[216.9,399.8],[224.4,410.2],[231.4,420.5],[238.4,431.2],[245.1,442.2],[251.5,453.1],[257.9,464.3],[263.9,475.6],[269.6,486.9],[275.2,498.4],[280.6,510],[285.7,521.5],[290.8,533],[295.8,544.2],[300.9,555.5],[305.8,566.5],[311,577.4],[316.1,588],[321.6,598.4],[327.2,608.8],[333.1,618.7],[339.3,628.7],[345.6,638.3],[352.1,648],[358.9,657.5],[365.9,666.9],[373,676.2],[380.4,685.4],[388,694.5],[395.7,703.5],[403.6,712.3],[411.7,721.1],[419.8,729.8],[428.1,738.3],[436.6,746.7],[445.2,754.9],[453.9,763],[462.7,770.8],[471.7,778.7],[480.6,786.3],[489.7,793.7],[499,801],[508.4,807.9],[517.9,814.8],[527.7,821.3],[537.5,827.7],[547.5,834],[557.7,839.9],[567.9,845.8],[578.4,851.5],[588.9,857],[599.6,862.4],[610.4,867.7],[621.2,872.8],[632.1,877.8],[643.1,882.7],[654.2,887.4],[665.3,892.1],[676.5,896.7],[687.7,901.2],[699.1,905.5],[710.3,909.7],[721.6,913.9],[733.1,918],[744.4,921.8],[755.9,925.7],[767.4,929.4],[779.1,932.8],[790.7,936.2],[802.3,939.6],[814.1,942.7],[826,945.8],[837.9,948.8],[849.9,952],[862,954.9],[874,958.1],[886.1,961.2],[898.1,964.3],[910.1,967.6],[922,970.7],[933.7,973.9],[945.4,977],[957,979.8],[968.5,982.5],[980,984.9],[991.5,987.1],[1003.1,988.9],[1014.7,990.6],[1026.5,992.1],[1038.3,993.3],[1050,994.5],[1062.1,995.5],[1074.1,996.3],[1086.2,997.2],[1098.4,997.9],[1110.5,998.6],[1122.7,999.2],[1134.9,999.7],[1147.1,1000.3],[1159.4,1000.6],[1171.6,1001],[1183.8,1001.3],[1196.2,1001.4],[1208.3,1001.6],[1220.5,1001.7],[1232.9,1001.7],[1245,1001.6],[1257.2,1001.4],[1269.4,1001.2],[1281.6,1000.9],[1293.8,1000.6],[1305.9,1000.2],[1317.9,999.7],[1329.8,999],[1341.6,998.3],[1353.2,997.5],[1364.8,996.3],[1376.2,994.9],[1387.7,993],[1398.9,991.1],[1410.2,988.6],[1421.7,985.9],[1433.2,983.1],[1444.8,980],[1456.6,976.8],[1468.5,973.6],[1480.6,970.4],[1492.8,967.5],[1505.1,964.5],[1517.4,961.6],[1529.7,958.9],[1542.1,956.4],[1554.4,953.8],[1566.6,951.3],[1578.6,948.6],[1590.7,945.8],[1602.7,943.1],[1614.7,940.3],[1626.4,937.5],[1638.2,934.5],[1650,931.3],[1661.7,928.1],[1673.5,924.8],[1685.3,921.5],[1697,918.1],[1708.8,914.6],[1720.4,911],[1732.2,907.3],[1743.8,903.6],[1755.6,899.8],[1767.2,895.9],[1778.9,892],[1790.5,888],[1802,883.9],[1813.6,879.7],[1825.1,875.6],[1836.6,871.4],[1848.1,867.1],[1859.6,862.7],[1870.9,858.1],[1882.4,853.6],[1893.7,849],[1905.2,844.3],[1916.6,839.7],[1927.9,835],[1939.3,830.1],[1950.5,825.3],[1961.8,820.3],[1972.9,815.5],[1984.1,810.4],[1995.2,805.4],[2006.1,800.1],[2017,794.9],[2027.8,789.5],[2038.6,784.1],[2049.3,778.4],[2059.8,772.7],[2070.3,766.9],[2080.6,761],[2091,754.9],[2101.4,748.8],[2111.8,742.7],[2122.1,736.4],[2132.3,730.2],[2142.7,723.8],[2152.9,717.4],[2163.3,711],[2173.5,704.4],[2183.8,697.8],[2194,690.9],[2204.2,684],[2214.3,676.9],[2224.3,669.8],[2234.2,662.2],[2244.2,654.7],[2254,647],[2263.8,639.2],[2273.4,631.2],[2283,623.3],[2292.5,615],[2301.9,606.8],[2311.1,598.3],[2320.1,589.6],[2328.8,580.6],[2337,571.4],[2344.8,561.9],[2351.9,552],[2358.2,542.5],[2363.7,533.4],[2368.4,524.8],[2371.8,518.2],[2374,513.5],[2375.9,509.1],[2377.5,505.1],[2378.2,503.3]]}},{"id":"argentine-lake-duck","kind":"specimen","common":"Argentine Lake Duck","scientific":"Oxyura vittata","group":"Birds","tags":["corkscrew","spines"],"measure":"Length of the inverted penis tube, base of cloaca to the bend of the loop (dissected)","state":"dissected","valueMm":223,"rangeMm":[190,245],"recordMm":425,"bodyMm":406,"bodyMeasure":"Total length of adult males (bill tip to tail tip): 40.6 cm, converted from the first of the two figures printed","confidence":"high","fact":"In five dissected males the penis averaged 22.3 cm. The spines near its base are sharp; further along they turn soft and brush-like.","marginNote":"The duck would like you to stop staring.","claims":[{"text":"Average length 22.3 cm (range 19.0–24.5 cm) in five males","source":1,"locator":"p.823","quote":"Total length of the penis tube as measured from the base of the cloaca to the bend of the loop was 22.3 ± 2.1 cm (range 19.0 to 24.5 cm; Fig. 1E). The width at the base … was 6.5 ± 1.3 mm (range 4.5 to 8 mm). From this point distally, the penis tapered gradually … the width of the penis tube was 3.4 ± 0.5 mm"},{"text":"Spines are sharp at the base, soft and brush-like distally, absent at the tip","source":1,"locator":"p.823","quote":"At the base of the penis (outer sheath), the spines are numerous, large, well developed, and sharp. As one proceeds distally, however, the spines diminish in number, become soft and brush-like, and take on a more ochre color, until at the distal terminus they disappear altogether"},{"text":"Duck penises spiral anticlockwise","source":3,"locator":"Fig. 1 caption","quote":"The male phallus (right) spirals in a counterclockwise direction"},{"text":"Record: a 42.5 cm penis photographed in a male Argentine lake duck","source":4,"locator":"Figure 1 caption","quote":"Photograph of the 42.5-cm penis of a male Argentine lake duck ( Oxyura vittata ) taken near Arroyo Chucul, Córdoba, Argentina on 30 April 2001."},{"text":"Corkscrew-shaped, almost half a metre, the largest of any bird measured so far (2001)","source":4,"locator":"Standfirst (abstract)","quote":"the penis of this small stifftail duck from South America is shaped like a corkscrew and, at almost half a metre long, is the largest of any bird measured so far."},{"text":"The penis is roughly half the body length","source":1,"locator":"p.823, Discussion","quote":"The penis of the Argentine Lake Duck measures approximately half the body length"},{"text":"Body mass of the five dissected males averaged 630 g","source":1,"locator":"p.821, Results","quote":"Mean body mass was 630 ± SD of 24 g (range 600 to 650 g)."},{"text":"In the related Muscovy duck, eversion takes about 0.36 s","source":3,"locator":"Abstract","quote":"Eversion of the 20 cm muscovy duck penis is explosive, taking an average of 0.36 s, and achieving a maximum velocity of 1.6 m s −1 ."}],"sources":[{"id":1,"label":"McCracken K.G. (2000) The 20-cm spiny penis of the Argentine Lake Duck (Oxyura vittata). The Auk 117(3):820–825","doi":"10.2307/4089612","url":"https://digitalcommons.usf.edu/auk/vol117/iss3/41","type":"peer-reviewed","verified":"2026-10-30, read from archived PDF of the original"},{"id":3,"label":"Brennan P.L.R., Clark C.J., Prum R.O. (2010) Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia. Proc. R. Soc. B 277:1309–1314","doi":"10.1098/rspb.2009.2139","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC2871948/","type":"peer-reviewed","verified":"2026-10-30, read from PMC full text"},{"id":4,"label":"McCracken K.G., Wilson R.E., McCracken P.J., Johnson K.P. (2001) Are ducks impressed by drakes' display? Nature 413:128","doi":"10.1038/35093160","url":"https://www.nature.com/articles/35093160","type":"peer-reviewed","verified":"2026-10-30, nature.com standfirst, Fig. 1 caption and Fig. 1 image read; the 1-page body text is paywalled (no OA/author copy found)"},{"id":5,"label":"Johnsgard P.A. (1978) Ducks, Geese, and Swans of the World. University of Nebraska Press. Tribe Oxyurini chapter (UNL DigitalCommons edition)","url":"https://digitalcommons.unl.edu/biosciducksgeeseswans/15","type":"monograph","verified":"2026-10-30, full text of the Oxyurini chapter PDF (Wayback copy of the UNL DigitalCommons file); page image checked for the '16\" (46 cm)' line"}],"imageRefs":[{"label":"McCracken et al. 2001, Nature 413:128, Fig. 1","what":"Photo of the 42.5 cm everted organ hanging from a dead male: a long narrow reddish tube twisted in a tight helix along most of its length, longer than the bird's body"},{"label":"McCracken 2000, Auk 117:822, Fig. 1E–F","what":"Tube proportions, taper, spine distribution (dissected, flaccid)"},{"label":"McCracken et al. 2001, Nature, Fig. 1","what":"Photograph of the everted 42.5 cm organ: helix along most of its length"}],"artNotes":"Length, widths, taper, spines and the basal flap follow McCracken 2000, who dissected O. vittata. The coil is measured off the only photograph of the everted organ (McCracken et al. 2001, Fig. 1): a short straight base, then a tight helix over about 91% of the length, loosest in the middle and tighter near the tip. The photo is low-resolution, so the 6.25 turns are approximate. You cannot tell from it which way the coil runs, so we assumed anticlockwise, as Brennan et al. (2010) report for other ducks. The reddish colour is from that photograph; McCracken 2000's greys and flesh tones describe the organ while it is still inverted inside the bird.","artSimplifications":["Spine count simplified","Apical coil radius and turn count illustrative"],"plate":{"src":{"256":"plates/argentine-lake-duck/256.webp","640":"plates/argentine-lake-duck/640.webp","1600":"plates/argentine-lake-duck/1600.webp","full":"plates/argentine-lake-duck/full.webp"},"w":2285,"h":190,"pxPerMm":10.2204,"a":[32.7,97.8],"b":[2239.3,88.6],"path":[[32.7,97.8],[44.1,97.8],[55.5,97.8],[66.9,97.8],[78.3,97.8],[89.7,97.8],[101.1,97.8],[112.4,97.8],[123.8,97.8],[135.2,97.8],[146.6,97.8],[158,97.8],[169.4,97.8],[180.8,97.8],[192.2,97.8],[203.6,97.8],[215,97.8],[226.4,97.8],[237.9,97.8],[246.2,97.2],[251,95.2],[256.4,91.3],[266.3,86.2],[281.7,82.3],[300.4,81.3],[319.5,81.4],[338.3,82.5],[356.3,84.5],[373.1,87.3],[388.1,90.7],[401.2,94.6],[412.4,98.4],[421.5,102.4],[428.7,106],[434,109.1],[438,111.6],[440.9,113.1],[443.3,113.7],[445.7,113.4],[448.5,112.3],[452.2,110.1],[457.1,107.2],[463.8,103.9],[472.3,100.2],[482.8,96.3],[495.3,92.6],[509.5,89.1],[525.6,86.3],[542.5,84.2],[559.7,83],[576.8,82.3],[593.5,82.3],[609.5,82.7],[624.9,83.4],[639.7,84.1],[654.2,85],[668.4,86.2],[682.2,87.4],[695.9,88.9],[708.9,90.3],[721.8,91.9],[734.2,93.6],[746.1,95.4],[757.7,97.1],[768.8,99],[779.5,100.7],[789.6,102.3],[799.5,103.9],[808.9,105.5],[818.1,106.8],[826.8,108.1],[835.3,109.2],[843.4,110.1],[851.5,110.9],[859.4,111.5],[867.1,111.9],[874.9,112.1],[882.5,112.1],[890.2,111.9],[897.9,111.5],[906,110.9],[914,110.1],[922.3,109.2],[930.9,108.1],[939.8,106.9],[949.1,105.6],[958.6,104.1],[968.5,102.6],[978.9,101.1],[989.6,99.4],[1000.8,97.8],[1012.3,96.2],[1024.3,94.6],[1036.5,93.1],[1049.3,91.7],[1062.3,90.2],[1075.7,89],[1089.3,87.9],[1103.3,86.9],[1117.5,86.1],[1131.7,85.4],[1146.2,85],[1160.7,84.6],[1175.4,84.5],[1189.9,84.6],[1204.4,84.9],[1218.9,85.3],[1233.1,85.9],[1247.2,86.6],[1261.2,87.5],[1274.8,88.6],[1288.2,89.8],[1301.2,91],[1314,92.3],[1326.4,93.8],[1338.3,95.2],[1350,96.7],[1361.3,98.3],[1372.1,99.8],[1382.7,101.1],[1392.8,102.6],[1402.7,103.9],[1412.3,105.1],[1421.4,106.1],[1430.4,107.2],[1439.3,108],[1447.9,108.7],[1456.4,109.2],[1464,109.7],[1470.9,109.9],[1476.9,109.7],[1482.1,108.9],[1487.3,107.3],[1493.1,104.8],[1500.2,101.5],[1509.6,97.9],[1521.6,94.2],[1535.9,90.9],[1552.1,88.3],[1569.9,86.6],[1588.2,86.1],[1606.6,86.6],[1624.1,88.3],[1640.3,90.9],[1654.4,94.2],[1666.3,97.6],[1675.8,101.2],[1683.1,104.4],[1688.5,106.9],[1692.5,108.5],[1695.9,109.1],[1699.3,108.5],[1703.4,106.8],[1709,104.4],[1716.5,101.2],[1726.2,97.9],[1738.2,94.4],[1752.2,91.4],[1768.2,89],[1785.5,87.4],[1803.4,86.9],[1821.3,87.4],[1838.4,89],[1854.4,91.4],[1868.3,94.4],[1880.3,97.8],[1889.8,101],[1897.4,103.9],[1903.4,106.3],[1908,107.7],[1912,108.3],[1916,107.7],[1920.8,106.1],[1926.9,103.9],[1934.6,101],[1944.5,97.8],[1956.5,94.7],[1970.4,91.9],[1986.2,89.7],[2002.9,88.2],[2020.5,87.8],[2037.9,88.2],[2054.6,89.7],[2070.3,91.9],[2084.1,94.7],[2095.9,97.8],[2105.7,100.7],[2113.8,103.5],[2120.1,105.6],[2125.3,106.9],[2130,107.3],[2134.6,106.9],[2140,105.5],[2146.4,103.3],[2154.6,100.7],[2164.6,97.8],[2176.6,95],[2190.4,92.3],[2205.7,90.3],[2222.2,89],[2239.3,88.6],[2239.3,88.6]]},"signatureAnimation":"corkscrew-uncoil","portrait":{"src":{"256":"portraits/argentine-lake-duck/256.webp","640":"portraits/argentine-lake-duck/640.webp","1200":"portraits/argentine-lake-duck/1200.webp"},"w":1881,"h":1050,"alt":"An Argentine lake duck drake, drawn side-on with his blue bill.","credit":"Drawn after a photo by Dude Daniels (Wikimedia Commons, CC BY-SA 3.0)."}},{"id":"ostrich","kind":"specimen","common":"Ostrich","scientific":"Struthio camelus","group":"Birds","tags":[],"measure":"Penis length in slaughtered ('obsolete') farm males aged 2–5 years, measured at dissection with a tape measure (erect/flaccid state not stated; post-mortem, so not erect). Range given is the range of age-class means (2–5 years), not of individual birds; SD from Table 2 (the text's ±12.45 cm is inconsistent with the table)","state":"dissected","valueMm":301,"rangeMm":[287,305],"confidence":"low","fact":"In male ostriches over two years old, measured at dissection, the penis averaged 30.1 cm. It is light red and shaped like an awl, with a groove along the back that carries semen.","marginNote":"It is the largest bird alive, which makes it slightly awkward that a duck from Argentina has it beaten.","claims":[{"text":"Average penis length 30.1 cm in ostriches over 2 years old","source":1,"locator":"p.182, §3.2 Penis","quote":"Table 2 indicates that the average weight of ostrich above 2 years old is 870±45.63g, and the length is 30.1±12.45cm."},{"text":"Age-class means: 20.7 cm at 1 yr, 28.7 cm at 2 yr, 30.4–30.5 cm at 3–5 yr; base diameter 6.26 cm, free-hanging portion 3.52 cm; colour light pink (1 yr) to light red","source":1,"locator":"p.184, Table 2","quote":"Table 2. The color and size of penis at different age stages of male ostrich … 1 120.7±6.11 13 20.7±1.15 4.16±0.21 2.53±0.09 12.96±0.67 Light pink; 2 140.1±7.31 8 28.7±1.24 5.31±0.20 3.12±0.10 15.73±0.84 Light red; 3 130.8±6.71 10 30.4±1.32 6.26±0.27 3.22±0.11 18.26±1.13 Light red; 4 130.8±5.79 12 30.5±1.28 6.34±0.31 3.53±0.09 20.19±1.27 Light red; 5 140.6±6.20 10 30.5±1.16 7.14±0.29 4.20±0.14 22.53±1.81 Light red; Average 135.6±6.50 10 30.1±1.25 6.26±0.29 3.52±0.11 19.18±1.26"},{"text":"Shape: base thick; free-hanging portion like a cone-helicoid, thinning from base to glans; deep groove on the back","source":1,"locator":"p.182, §3.2 Penis","quote":"The penis is divided into two parts, the base and the free hanging portion. The base of the penis is thick. … The free-hanging portion of the ostrich is like a cone-helicoid, and becomes thinner from base to glans. There is a 19.18±3.58mm deep Penis … groove at the back. It is closed like a tube while mating"},{"text":"Looks like an awl, 25–30 cm in adults","source":1,"locator":"p.182, §4 Discussion","quote":"The penis of the ostrich is very strong. An adult ostrich’s penis can be as long as 25-30cm and looks like an awl."},{"text":"Measured by dissection of slaughtered birds","source":1,"locator":"p.181–182, §2.2–2.3 Devices and Methods","quote":"Sharp knife, tulwar, scalpel, scissors, tweezers, hemostat, tape measure, electronic scale and animal operating table. … Firstly, bleed the heart of the chosen ostriches until all the blood was left out. Secondly, pluck, unplug the skin and meat. Thirdly, remove all of the inner organs. Then systematic anatomic observation on the whole reproductive system was carried out."},{"text":"Flaccid, the ostrich penis can be as long as 20 cm and is bright red (King 1981)","source":2,"locator":"p.821","quote":"The penis of an Ostrich (Struthio camelus), for example, can measure as long as 20 cm when flaccid and is bright red in color (King 1981)."},{"text":"Ratites are among the few bird groups with a well-developed copulatory organ","source":2,"locator":"p.820","quote":"Several groups of birds, including ratites, screamers, waterfowl, and cracids, possess well-developed male copulatory organs (Forbes 1882, King 1981, Lake 1981)."},{"text":"Flaccid up to 20 cm, folded in a pocket in the cloaca; erect it may reach 40 cm and deviates to the left; no urinary function","source":3,"locator":"Reproductive system section (p.75–82 chapter)","quote":"In adult ostrich males, the flaccid phallus is up to 20 cm long and lies folded in a phallic pocket in the ventral wall of the proctodeum; when erect, it may reach a length of 40 cm and physiologically deviates to the left. 18 , 53 It serves to transport sperm via a dorsal sulcus (in the ostrich and kiwi) or a central cavity (in the rhea, emu, cassowary) but has no urinary function."},{"text":"Adult phallus is J-shaped and curves to the left when everted","source":4,"locator":"p.1291 (Reproductive anatomy); Fig. 48.11 on p.1296","quote":"The phallus of the adult male ostrich is “J”-shaped and when everted curves to the left (Figure 48.11)."},{"text":"The ostrich is the largest living bird, over 200 kg and 2.7 m tall","source":4,"locator":"p.1285","quote":"The ostrich is the largest living bird, reaching over 200 kg in weight and 2.7 m in height."},{"text":"Phallus carries semen in a dorsal groove and has no urinary function","source":4,"locator":"p.1290","quote":"the phallus contains a dorsal groove through which the semen travels (Figure 48.9).19 The avian phallus serves no function within the urinary system and does not contain a urethra."},{"text":"The Argentine lake duck's penis (42.5 cm photographed) is the largest of any bird measured so far","source":5,"locator":"Standfirst; Figure 1 caption","quote":"the penis of this small stifftail duck from South America is shaped like a corkscrew and, at almost half a metre long, is the largest of any bird measured so far. … Photograph of the 42.5-cm penis of a male Argentine lake duck ( Oxyura vittata )"}],"sources":[{"id":1,"label":"Zhang Y., Ren Z., Tang L. (2011) Anatomic study on the main male reproductive organs of ostrich. Global Journal of Health Science 3(1):181–184","doi":"10.5539/gjhs.v3n1p181","url":"https://ccsenet.org/journal/index.php/gjhs/article/view/10063","type":"peer-reviewed","verified":"2026-10-30, full text PDF (CC BY). Note SD inconsistency between text (±12.45 cm) and Table 2 (±1.25 cm)"},{"id":2,"label":"McCracken K.G. (2000) The 20-cm spiny penis of the Argentine Lake Duck (Oxyura vittata). The Auk 117(3):820–825","doi":"10.2307/4089612","url":"https://digitalcommons.usf.edu/auk/vol117/iss3/41","type":"peer-reviewed","verified":"2026-10-30, full text (Wayback copy of the USF DigitalCommons PDF)"},{"id":3,"label":"Kummrow M.S. (2015) Ratites or Struthioniformes: Struthiones, Rheae, Cassuarii, Apteryges (ostriches, rheas, emus, cassowaries, and kiwis), and Tinamiformes (tinamous). In Miller R.E., Fowler M.E. (eds) Fowler's Zoo and Wild Animal Medicine, Vol. 8, pp.75–82. Elsevier","doi":"10.1016/B978-1-4557-7397-8.00009-8","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC7152070/","type":"book","verified":"2026-10-30, full text via Europe PMC (Elsevier COVID-19 collection)"},{"id":4,"label":"Chapter 48 'Ratites' in Ritchie B.W., Harrison G.J., Harrison L.R. (eds) (1994) Avian Medicine: Principles and Application, pp.1284–1328. Wingers Publishing (chapter author not printed in the hosted PDF)","url":"https://www.harrisonsbirdfoods.com/wp-content/uploads/2024/03/1284-1328-Ch48-Ratites.pdf","type":"book","verified":"2026-10-30, full text PDF hosted by Harrison's Bird Foods"},{"id":5,"label":"McCracken K.G., Wilson R.E., McCracken P.J., Johnson K.P. (2001) Are ducks impressed by drakes' display? Nature 413:128","doi":"10.1038/35093160","url":"https://www.nature.com/articles/35093160","type":"peer-reviewed","verified":"2026-10-30, standfirst and Fig. 1 caption on nature.com; body text paywalled"}],"imageRefs":[{"label":"Ritchie et al. 1994, Ch. 48 Ratites, Fig. 48.11","what":"Left lateral line drawing of the cloaca with retracted phallus and the erect phallus (8) with dorsal sulcus (7): long, tapering, J-curved"},{"label":"Ritchie et al. 1994, Ch. 48 Ratites, Fig. 48.10a","what":"Photo of the erect phallus of a 3-month-old male: firm, conical, curving left, prominent seminal groove (juvenile)"},{"label":"Zhang et al. 2011, Fig. 2","what":"Dissected cloaca with the penis (A); light-red tissue colour"}],"artNotes":"Outline from Ritchie et al. Fig. 48.11 (erect phallus, side view), with widths from Zhang 2011 Table 2. The twist in the free part is described only in words ('cone-helicoid'), so it is drawn lightly. The headline length was taken after death, at dissection, so the J-curve here belongs to a different state, the erect and everted one.","artSimplifications":["Twist of the free-hanging portion illustrative (described, not figured)","Surface texture omitted"],"plate":{"src":{"256":"plates/ostrich/256.webp","640":"plates/ostrich/640.webp","1600":"plates/ostrich/1600.webp","full":"plates/ostrich/full.webp"},"w":2418,"h":800,"pxPerMm":8.1476,"a":[288,127.4],"b":[2369.9,693.4],"path":[[288,127.4],[274.9,166.3],[266.2,206.4],[262.2,247.1],[262.7,288.1],[267.8,328.9],[277.5,368.7],[291.5,407.2],[309.9,443.8],[332.2,478.2],[358.2,509.7],[387.6,538.1],[419.9,562.9],[455,583.9],[492.1,600.8],[530.8,613.3],[570.8,621.4],[611.4,624.8],[652.1,626.5],[692.8,628],[733.5,629.6],[774.2,631.2],[814.9,632.8],[855.6,634.4],[896.3,636],[937,637.5],[977.7,639.1],[1018.4,640.8],[1059.1,642.3],[1099.8,643.9],[1140.5,645.4],[1181.2,647],[1221.9,648.7],[1262.6,650.2],[1303.3,651.8],[1344,653.4],[1384.7,655],[1425.4,656.6],[1466.2,658.2],[1506.9,659.7],[1547.6,661.3],[1588.3,663],[1629,664.5],[1669.7,666.1],[1710.4,667.6],[1751.1,669.2],[1791.8,670.9],[1832.6,672.4],[1873.3,674],[1914,675.5],[1954.7,677.2],[1995.4,678.8],[2036.1,680.4],[2076.8,681.9],[2117.5,683.5],[2158.3,685.2],[2199,686.7],[2239.7,688.3],[2280.4,689.8],[2321.1,691.4],[2361.8,693.1],[2369.9,693.4]]},"portrait":{"src":{"256":"portraits/ostrich/256.webp","640":"portraits/ostrich/640.webp","1200":"portraits/ostrich/1200.webp"},"w":1237,"h":1997,"alt":"A male ostrich, drawn side-on.","credit":"Drawn after a photo by Charles J. Sharp (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"domestic-pig","kind":"specimen","common":"Pig (boar)","scientific":"Sus scrofa domesticus","group":"Mammals","tags":["corkscrew"],"measure":"Total length of the adult boar's penis as given in a veterinary anatomy textbook ('resembles in general that of the ox', 45–50 cm); endpoints, method and state not stated","state":"unknown","valueMm":475,"rangeMm":[450,500],"bodyMm":1520,"bodyMeasure":"Average body length of adult boars of the Krškopolje breed (Slovenian local breed, adult males ~280 kg), tip of the nose to the base of the tail. Different population from the Sisson penis figure; n not stated","confidence":"medium","fact":"A boar's penis, 45–50 cm long, has no glans. Its front end is twisted into a spiral, usually called the corkscrew.","marginNote":"Engineered for a threaded connection.","claims":[{"text":"Adult length about 45–50 cm","source":1,"locator":"p. 592","quote":"The penis in the adult boar measures about 18 to 20 inches (ca. 45 to 50 cm.) in length."},{"text":"No glans; the front part is spirally twisted, especially in erection; the sigmoid flexure lies in front of the scrotum","source":1,"locator":"p. 592","quote":"The penis resembles in general that of the ox. The sigmoid flexure is, however, prescrotal. The anterior part has no glans, and is spirally twisted, especially in erection."},{"text":"Slit-like urethral opening on the side, near the pointed tip","source":1,"locator":"p. 592","quote":"The external urethral orifice is slit-like and is situated ventro-laterally, close to the pointed extremity."},{"text":"The corkscrew end is matched by ridges in the sow's cervix that sense stimulation from the penis","source":2,"locator":"section 'Female choice'","quote":"Male pigs have penises that end on a corkscrew filament whereas sows have ridges on their cervix that specifically sense stimulation from the penis during copulation."},{"text":"In artificial insemination the cervical ridges must be stimulated or pregnancy rates drop","source":2,"locator":"section 'Female choice'","quote":"When sows are artificially inseminated, stimulation of the cervix ridges must occur otherwise the pregnancy rates drop dramatically ( Bonet et al. 2013 )."},{"text":"Adult Krškopolje boars average 152 cm from nose to tail base and weigh about 280 kg (used for Relative mode)","source":3,"locator":"Table 1 and footnote 1","quote":"Body weight (kg) 280 230 · Body length¹ (cm) 152 140 … ¹ Measured from the tip of the nose to the starting point of the tail."}],"sources":[{"id":1,"label":"Sisson S. (1914) The Anatomy of the Domestic Animals. 2nd ed., entirely reset. Philadelphia & London: W. B. Saunders Company. Genital organs of the boar, pp. 591–592; Fig. 527 (after Ellenberger-Baum)","url":"https://archive.org/details/cu31924001263270","type":"book","verified":"2026-10-30, full text (archive.org OCR of two copies, checked against page image of p. 592); same wording in 4th ed. 1953, p. 602"},{"id":2,"label":"Brennan P.L.R., Prum R.O. (2015) Mechanisms and evidence of genital coevolution: the roles of natural selection, mate choice, and sexual conflict. Cold Spring Harb. Perspect. Biol. 7:a017749","doi":"10.1101/cshperspect.a017749","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC4484975/","type":"peer-reviewed","verified":"2026-10-30, PMC full text"},{"id":3,"label":"Batorek-Lukač N., Tomažin U., Škrlep M., Kastelic A., Poklukar K., Čandek-Potokar M. (2019) Krškopoljski prašič (Krškopolje pig). In: Čandek-Potokar M., Nieto Liñán R.M. (eds) European Local Pig Breeds – Diversity and Performance. A study of project TREASURE. IntechOpen, London (open-access peer-reviewed chapter)","doi":"10.5772/intechopen.83767","url":"https://www.intechopen.com/chapters/65260","type":"monograph","verified":"2026-10-30, full text (IntechOpen HTML chapter, Table 1). For comparison, the same book's Lithuanian White (old type) chapter (doi 10.5772/intechopen.83771, Table 1) gives adult boars 299 kg and 170.4 cm, but measured from the back of the head (head excluded), so it was not used"}],"imageRefs":[{"label":"Sisson 1914, Fig. 527 (p. 592): Genital organs of boar, l'' = spiral anterior part of penis exposed by slitting the prepuce","what":"Overall course of the penis with prescrotal sigmoid flexure and the spiral front part (small, schematic)"},{"label":"Wikimedia Commons, 'Semen Collecting From Boar.JPG' (user Dingar, public domain)","what":"Photo of the erect, exteriorised spiral front part during semen collection: pink colour, tightness of the twist, taper. No scale."}],"artNotes":"Drawn straightened, as in erection, with the true-size length running root to tip over the whole 45–50 cm. The spiral is confined to the front part, as Sisson describes, and the plate is tilted slightly so the helix shows. No source gives the direction or number of turns, so the 2.5 turns, radius, pitch and handedness are our own choice.","artSimplifications":["Spiral turn count, pitch and handedness illustrative (not given in sources)","Root muscles simplified"],"plate":{"src":{"256":"plates/domestic-pig/256.webp","640":"plates/domestic-pig/640.webp","1600":"plates/domestic-pig/1600.webp","full":"plates/domestic-pig/full.webp"},"w":2384,"h":220,"pxPerMm":4.8517,"a":[98.8,112.5],"b":[2354.1,112.5],"path":[[98.8,112.5],[280.7,112.5],[462.7,112.5],[644.6,112.5],[826.6,112.5],[1008.5,112.5],[1190.5,112.5],[1372.4,112.5],[1554.2,112.5],[1736.2,112.5],[1918.1,112.5],[1919.5,112.5],[1920.8,112.5],[1922,112.4],[1923.4,112.4],[1924.6,112.2],[1926,112.1],[1927.3,111.9],[1928.7,111.6],[1929.9,111.5],[1931.3,111.2],[1932.7,111.1],[1933.9,110.8],[1935.3,110.5],[1936.7,110.2],[1938.1,109.8],[1939.6,109.5],[1941,109.2],[1942.4,108.9],[1943.9,108.5],[1945.3,108.2],[1946.8,107.8],[1948.3,107.5],[1949.9,107.1],[1951.4,106.8],[1952.9,106.5],[1954.6,106.1],[1956.1,105.8],[1957.8,105.5],[1959.3,105.2],[1960.9,104.9],[1962.6,104.8],[1964.3,104.5],[1965.9,104.3],[1967.6,104.2],[1969.3,104],[1971.1,103.9],[1972.7,103.9],[1974.4,103.8],[1976.2,103.8],[1977.9,103.8],[1979.7,103.9],[1981.3,104],[1983.1,104.2],[1984.9,104.3],[1986.6,104.5],[1988.4,104.8],[1990,105.1],[1991.9,105.5],[1993.5,105.8],[1995.3,106.2],[1997,106.6],[1998.6,107.2],[2000.3,107.8],[2002.1,108.3],[2003.8,108.9],[2005.3,109.6],[2007,110.2],[2008.6,110.9],[2010.1,111.8],[2011.8,112.5],[2013.2,113.2],[2014.6,114.1],[2016,114.8],[2017.3,115.7],[2018.6,116.4],[2020,117.1],[2021.2,117.9],[2022.5,118.7],[2023.7,119.4],[2025,120.1],[2026.2,120.7],[2027.3,121.4],[2028.6,122],[2029.7,122.5],[2030.8,123.1],[2031.9,123.7],[2033,124.2],[2034.1,124.7],[2035.2,125.1],[2036.3,125.5],[2037.3,126],[2038.4,126.3],[2039.4,126.5],[2040.5,126.8],[2041.5,127],[2042.4,127.3],[2043.5,127.4],[2044.5,127.4],[2045.5,127.5],[2046.6,127.5],[2047.6,127.5],[2048.5,127.4],[2049.5,127.4],[2050.6,127.3],[2051.6,127],[2052.7,126.8],[2053.7,126.5],[2054.6,126.3],[2055.7,126],[2056.8,125.5],[2057.8,125.1],[2058.9,124.7],[2060,124.2],[2061.1,123.7],[2062.2,123.1],[2063.4,122.5],[2064.6,122],[2065.7,121.4],[2067,120.7],[2068.1,120.1],[2069.3,119.4],[2070.6,118.7],[2071.8,117.9],[2073.2,117.1],[2074.4,116.4],[2075.8,115.7],[2077.2,114.8],[2078.5,114.1],[2079.8,113.2],[2081.4,112.5],[2082.8,111.8],[2084.3,110.9],[2085.7,110.2],[2087.2,109.3],[2088.7,108.6],[2090.2,107.9],[2091.9,107.1],[2093.4,106.3],[2095.1,105.6],[2096.6,104.9],[2098.3,104.3],[2099.9,103.6],[2101.6,103],[2103.4,102.5],[2105.1,101.9],[2106.7,101.3],[2108.5,100.8],[2110.3,100.3],[2112.1,99.9],[2113.8,99.5],[2115.6,99],[2117.4,98.7],[2119.2,98.5],[2121.1,98.2],[2122.9,98],[2124.7,97.7],[2126.5,97.6],[2128.5,97.6],[2130.3,97.5],[2132.1,97.5],[2134,97.5],[2135.8,97.6],[2137.6,97.6],[2139.4,97.7],[2141.4,98],[2143.2,98.2],[2145,98.5],[2146.8,98.7],[2148.6,99],[2150.4,99.5],[2152.2,99.9],[2154,100.3],[2155.6,100.8],[2157.4,101.3],[2159.1,101.9],[2160.9,102.5],[2162.6,103],[2164.2,103.6],[2165.9,104.3],[2167.6,104.9],[2169.2,105.6],[2170.8,106.3],[2172.4,107.1],[2173.9,107.9],[2175.5,108.6],[2177,109.3],[2178.5,110.2],[2180,110.9],[2181.4,111.8],[2182.9,112.5],[2184.3,113.2],[2185.7,114.1],[2187.1,114.8],[2188.5,115.7],[2189.7,116.4],[2191.1,117.1],[2192.4,117.9],[2193.6,118.7],[2194.9,119.4],[2196.1,120.1],[2197.4,120.7],[2198.5,121.4],[2199.7,122],[2200.8,122.5],[2201.9,123.1],[2203,123.7],[2204.1,124.2],[2205.3,124.7],[2206.4,125.1],[2207.5,125.5],[2208.4,126],[2209.6,126.3],[2210.5,126.5],[2211.6,126.8],[2212.6,127],[2213.7,127.3],[2214.7,127.4],[2215.7,127.4],[2216.8,127.5],[2217.7,127.5],[2218.7,127.5],[2219.7,127.4],[2220.8,127.4],[2221.7,127.3],[2222.7,127],[2223.8,126.8],[2224.8,126.5],[2225.9,126.3],[2226.9,126],[2228,125.5],[2229.1,125.1],[2230.1,124.7],[2231.2,124.2],[2232.3,123.7],[2233.4,123.1],[2234.6,122.5],[2235.7,122],[2236.9,121.4],[2238.1,120.7],[2239.3,120.1],[2240.6,119.4],[2241.8,118.7],[2243.1,117.9],[2244.3,117.1],[2245.6,116.4],[2247,115.7],[2248.4,114.8],[2249.7,114.1],[2251.1,113.2],[2252.5,112.5],[2253.9,111.8],[2255.4,110.9],[2256.8,110.2],[2258.3,109.3],[2259.9,108.6],[2261.4,107.9],[2263,107.1],[2264.6,106.3],[2266.2,105.6],[2267.9,104.9],[2269.4,104.3],[2271.1,103.6],[2272.9,103],[2274.5,102.5],[2276.2,101.9],[2278,101.3],[2279.7,100.8],[2281.5,100.3],[2283.3,99.9],[2285.1,99.5],[2286.9,99],[2288.7,98.7],[2290.5,98.5],[2292.3,98.2],[2294.1,98],[2295.9,97.7],[2297.8,97.6],[2299.6,97.6],[2301.4,97.5],[2303.2,97.5],[2305.2,97.5],[2307,97.6],[2308.8,97.6],[2310.7,97.7],[2312.5,98],[2314.3,98.2],[2316.1,98.5],[2317.9,98.7],[2319.7,99],[2321.5,99.5],[2323.3,99.9],[2325.1,100.3],[2326.9,100.8],[2328.6,101.3],[2330.4,101.9],[2332.1,102.5],[2333.7,103],[2335.4,103.6],[2337,104.3],[2338.7,104.9],[2340.4,105.6],[2342,106.3],[2343.6,107.1],[2345.1,107.9],[2346.7,108.6],[2348.3,109.3],[2349.7,110.2],[2351.2,110.9],[2352.7,111.8],[2354.1,112.5],[2354.1,112.5]]},"portrait":{"src":{"256":"portraits/domestic-pig/256.webp","640":"portraits/domestic-pig/640.webp","1200":"portraits/domestic-pig/1200.webp"},"w":2025,"h":1128,"alt":"A Krškopolje boar, black with a white belt, drawn side-on.","credit":"Drawn after a photo by Andrej Kastelic (Wikimedia Commons, CC BY-SA 3.0)."}},{"id":"tapir","kind":"specimen","common":"Lowland tapir","scientific":"Tapirus terrestris","group":"Mammals","tags":[],"measure":"Penis length, 'from the bulbourethral gland to the tip of the glans' as reported in a species account; number of animals, state and original source not stated","state":"unknown","valueMm":490,"bodyMm":2040,"bodyMeasure":"Upper end of the reported range of total body length for males (a maximum, not a mean)","confidence":"low","fact":"Writing in 1831, Richard Owen described the American tapir's penis only as 'of great length'. A later species account gives 49 cm, from the bulbourethral gland to the tip.","marginNote":"Owen got the ruler out for the caecum, but not for this.","claims":[{"text":"49 cm from the bulbourethral gland to the tip of the glans (T. terrestris)","source":1,"locator":"p. 3","quote":"The penis measures 49 cm from the bulbourethral gland to the tip of the glans."},{"text":"Owen (1831) described the American tapir's penis as 'of great length', ending in an enlarged, flat-ended disc with the urethral opening near its lower edge","source":2,"locator":"p. 163","quote":"The penis, of great length, terminates in an enlarged truncate extremity, the orifice of the urethra being near the lower margin of the disc."},{"text":"Owen found no levator muscles; elastic tissue runs along the top of the penis","source":2,"locator":"p. 163","quote":"There are no levatores muscles ; but a quantity of elastic cellular membrane extends from the abdominal muscles along the dorsum penis."},{"text":"In the Malayan tapir, there is one dorsal and two lateral projections just behind the glans","source":3,"locator":"Abstract","quote":"The penis has one dorsal and two lateral penile projections just proximal to the glans penis."},{"text":"In a young Malayan tapir, the glans was conical with a squarish fold behind it","source":4,"locator":"p. 773, Fig. 4","quote":"behind the glans there was a squarish forwardly directed fold. The glans was conical ; and the lower lip of the urethral aperture projected slightly."},{"text":"Owen gave the caecum's measurements but no length for the penis","source":2,"locator":"p. 163","quote":"in the American Tapir the length of the cæcum was 1 foot 3 inches, its greatest breadth 1 foot."}],"sources":[{"id":1,"label":"Padilla M., Dowler R.C. (1994) Tapirus terrestris. Mammalian Species 481:1–8. American Society of Mammalogists","doi":"10.2307/3504109","url":"https://web.archive.org/web/20160303194758/http://www.science.smith.edu/msi/pdf/i0076-3519-481-01-0001.pdf","type":"monograph","verified":"2026-10-30, full scanned PDF (Wayback copy of the Smith College Mammalian Species archive), read from page images"},{"id":2,"label":"Owen R. (1831) [Notes on the anatomy of the American Tapir, Tapir americanus]. Proceedings of the Committee of Science and Correspondence of the Zoological Society of London 1:162–164 (meeting of 13 Dec. 1831)","url":"https://archive.org/details/proceedingsofcom183032zool","type":"other","verified":"2026-10-30, full text OCR and page image of p. 163 (archive.org)"},{"id":3,"label":"Lilia K., Rosnina Y., Abd Wahid H., Zahari Z.Z., Abraham M. (2010) Gross anatomy and ultrasonographic images of the reproductive system of the Malayan tapir (Tapirus indicus). Anat. Histol. Embryol. 39(6):569–575","doi":"10.1111/j.1439-0264.2010.01030.x","type":"peer-reviewed","verified":"2026-10-30, abstract only (Europe PMC); full text paywalled, not read"},{"id":4,"label":"Parker W.N. (1882) On some points in the anatomy of the Indian tapir (Tapirus indicus). Proc. Zool. Soc. London 1882:768–777","doi":"10.1111/j.1096-3642.1883.tb02796.x","url":"https://archive.org/details/biostor-108482","type":"peer-reviewed","verified":"2026-10-30, full text (archive.org/BioStor OCR and page images)"}],"imageRefs":[{"label":"Parker 1882, Fig. 4 (p. 773): Upper surface of penis of a young Indian tapir, one half natural size","what":"Distal part only, from above: conical glans and the fold behind it. Different species and an immature animal."},{"label":"Wikimedia Commons, 'Tapir male walks away dragging penis.jpg' (Erik Terdal, 2013, CC BY-SA 2.0)","what":"Live male with the penis extended to the ground: overall length relative to the legs, pink colour, enlarged blunt tip. Species not stated on the file page; no scale."}],"artNotes":"The plate spans the whole 49 cm, from the bulbourethral gland to the glans tip, so it includes the internal part as well as what shows outside. The tip disc and its three projections combine two species: Owen's description of the American tapir (T. terrestris) and Lilia et al.'s of the Malayan tapir (T. indicus). Shaft width is not sourced; we chose it.","artSimplifications":["Shaft width illustrative (no sourced diameter)","Tip morphology combined from T. terrestris (Owen) and T. indicus (Lilia et al.)"],"plate":{"src":{"256":"plates/tapir/256.webp","640":"plates/tapir/640.webp","1600":"plates/tapir/1600.webp","full":"plates/tapir/full.webp"},"w":2417,"h":337,"pxPerMm":4.8233,"a":[25.6,169.5],"b":[2389,169.5]},"portrait":{"src":{"256":"portraits/tapir/256.webp","640":"portraits/tapir/640.webp","1200":"portraits/tapir/1200.webp"},"w":2076,"h":1261,"alt":"A lowland tapir, drawn side-on, short trunk and all.","credit":"Drawn after a photo by Charles J. Sharp (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"horse","kind":"specimen","common":"Horse (stallion)","scientific":"Equus caballus","group":"Mammals","tags":[],"measure":"Total length of the non-erect ('quiescent') penis including the root (ischial arch to glans); of this, about 15–20 cm is the free part inside the prepuce","state":"flaccid","valueMm":500,"bodyMm":1569,"bodyMeasure":"Trunk length, point of shoulder (caput humeri) to point of buttock (tuber ischii), excluding head and neck; 24 Thoroughbreds aged 4–16, sex not stated","confidence":"medium","fact":"A stallion's penis is about 50 cm long when not erect, counting the root. Erection adds at least half as much again, and the glans swells more than the rest.","marginNote":"The horse would like it noted that this is the relaxed figure.","claims":[{"text":"About 50 cm long when not erect, 15–20 cm of it free in the prepuce","source":1,"locator":"p. 580","quote":"In the quiescent state it is about 20 inches (ca. 50 cm.) long; of this, about 6 to 8 inches (ca. 15 to 20 cm.) is free in the prepuce."},{"text":"Erection adds 50% or more to the length","source":1,"locator":"p. 580","quote":"In erection it increases 50 per cent. or more in length."},{"text":"An extension source says erection doubles length and thickness, and the glans grows 3–4 times","source":2,"locator":"p. 2 (PDF p. 3), 'Penis' paragraph","quote":"When not erect, the penis is 50 cm long and 2.5 to 6 cm in diameter with the distal end 15 to 20 cm free in the prepuce. When erect, the penis doubles in length and thickness and the glans increases by 3 to 4 times."},{"text":"Glans is the enlarged free end, with a prominent toothed rim (corona glandis)","source":1,"locator":"pp. 580–581","quote":"The glans penis is the enlarged free end of the organ. Its anterior surface or base is surrounded by a prominent, denticulated margin, the corona glandis."},{"text":"The urethra protrudes about 2.5 cm as a free tube (urethral process) from a pit in the glans","source":1,"locator":"p. 581","quote":"the fossa glandis, in which the urethra protrudes for about an inch (ca. 2.5 cm.) as a free tube, the urethral process (Processus urethræ), covered by a thin integument."},{"text":"Body is laterally flattened, becoming rounded and smaller towards the front","source":1,"locator":"p. 580","quote":"This part of the penis is flattened laterally for the most part, but becomes rounded and smaller anteriorly."},{"text":"The glans reaches full size later in erection than the shaft","source":1,"locator":"p. 582, footnote 1","quote":"This may account for the fact that the glans reaches its extreme size during erection later than the corpus cavernosum penis."}],"sources":[{"id":1,"label":"Sisson S. (1914) The Anatomy of the Domestic Animals. 2nd ed., entirely reset. Philadelphia & London: W. B. Saunders Company. Genital organs of the stallion: The penis, pp. 580–582; Fig. 518","url":"https://archive.org/details/cu31924001263270","type":"book","verified":"2026-10-30, full text (archive.org OCR, checked against page image of p. 580); same wording in 4th ed. 1953, p. 590"},{"id":2,"label":"Equine Section, Department of Animal Sciences, University of Kentucky (1988) The Stallion: Breeding Soundness Examination & Reproductive Anatomy. Cooperative Extension Service publication ASC-117","url":"https://uknowledge.uky.edu/anr_reports/16","type":"other","verified":"2026-10-30, full PDF via Wayback Machine (id_ snapshot 20240713)"},{"id":3,"label":"Ünal N., Paksoy Y., Güngör Ö.F. (2025) Agreement of the morphometric dimensions determined by traditional and image analysis methods for Arabian and Thoroughbred horses. Arch. Anim. Breed. 68:253–261","doi":"10.5194/aab-68-253-2025","url":"https://aab.copernicus.org/articles/68/253/2025/","type":"peer-reviewed","verified":"2026-10-30, full text PDF (open access)"}],"imageRefs":[{"label":"Sisson 1914, Fig. 518 (p. 580): Penis of horse; lateral view","what":"Whole non-erect organ from root (tuber ischii) to glans: laterally flattened body, collum and corona glandis, urethral process"}],"artNotes":"Traced from the non-erect organ in Sisson Fig. 518, side view. The true-size length runs from the root at the ischial arch to the tip of the urethral process, matching the 50 cm total. Pelvis, arteries and labels are left out. We did not draw an erect, flared glans because we found no measured erect figure.","artSimplifications":["Surrounding pelvis, vessels and muscles omitted","Surface striations simplified"],"plate":{"src":{"256":"plates/horse/256.webp","640":"plates/horse/640.webp","1600":"plates/horse/1600.webp","full":"plates/horse/full.webp"},"w":2472,"h":611,"pxPerMm":5.3125,"a":[43.4,56.5],"b":[2445.9,328.3],"path":[[43.4,56.5],[48.3,104.4],[56.8,170.3],[71.1,228.7],[90.4,284.5],[117.6,331.6],[155.4,365.5],[200.8,389.2],[248.9,400.9],[300.1,398.6],[356.3,397],[411.9,404.9],[476.9,414.9],[576.3,420.2],[710.6,421.8],[850.3,421.7],[982,419.8],[1113.8,416.7],[1245.5,413.5],[1377.3,410.4],[1509,406.9],[1644.6,404.6],[1777.7,401.2],[1894.6,390.6],[1997.5,372.9],[2085.2,354.5],[2154,337.5],[2208.6,321.5],[2257,310],[2297.4,302.1],[2332.3,298.8],[2361.8,301.7],[2386.7,308.6],[2409.6,315.3],[2431,322.7],[2445.9,328.3],[2445.9,328.3]]},"portrait":{"src":{"256":"portraits/horse/256.webp","640":"portraits/horse/640.webp","1200":"portraits/horse/1200.webp"},"w":2030,"h":1454,"alt":"A bay Thoroughbred stallion, drawn side-on.","credit":"Drawn after a public-domain photo of the stallion Bay Ronald (Wikimedia Commons, public domain)."}},{"id":"walrus","kind":"specimen","common":"Pacific walrus (baculum)","scientific":"Odobenus rosmarus divergens","group":"Mammals","tags":["baculum","record-holder"],"measure":"Length of the dried, cleaned baculum (os penis) of adult males aged 15 years or older; the bone only, not the soft penis","state":"bone","valueMm":559,"rangeMm":[476,622],"recordMm":624,"bodyMm":3200,"bodyMeasure":"Mean standard length (snout to tail tip, straight line, on the back) of adult males older than 14 years, n = 55, range 279–356 cm","confidence":"high","fact":"The penis bone of an adult Pacific walrus averages 55.9 cm. Fay's 1982 monograph calls it the largest baculum of any living mammal, both absolutely and for the size of the animal.","marginNote":"Walrus sold separately.","claims":[{"text":"Adult (15+ years) baculum 47.6–62.2 cm, mean 55.9 cm, n = 43","source":1,"locator":"p. 35","quote":"In 43 adults that were 15 years old or older, the length of the os penis ranged from 47.6 to 62.2 cm (mean, 55.9 cm)"},{"text":"Longest baculum recorded: 62.4 cm","source":1,"locator":"p. 36","quote":"The longest baculum, from an animal of unknown age, was 62.4 cm; the heaviest weighed 1,070 g."},{"text":"Largest baculum of any living mammal, absolutely and relative to body; about 18% of standard length","source":1,"locator":"p. 36","quote":"In actual size, as well as in relation to the body, the baculum of the adult Pacific walrus is the largest in any living mammal, being equal to about 18 % of the standard length and about 0.1 % of the whole body weight (Scheffer and Kenyon 1963)."},{"text":"Adult baculum weighs 489–1,040 g (mean 874 g)","source":1,"locator":"pp. 35–36","quote":"weights (Fig. 22) were from 489 to 1,040 g (mean, 874.1 g)."},{"text":"In newborn calves the bone is about 10.6 cm; it grows 5.3 times in length to adulthood","source":1,"locator":"pp. 35–36","quote":"Sixty-six of the bacula were from calves less than 1 month old. In that age group, length of baculum ranged from 9.2 to 12.8 cm (mean, 10.6 cm)"},{"text":"The penis lies in an abdominal sheath, and more than half of its bulk is bone","source":1,"locator":"p. 175","quote":"The penis lies in an abdominal sheath, and in the adult more than half of its bulk is made up of bone, the os penis or baculum."},{"text":"Measured on cleaned, air-dried bones from 273 males killed at St. Lawrence Island","source":1,"locator":"p. 35","quote":"I obtained the baculum or os penis from 273 males killed at St. Lawrence Island during the months of May and June. These were fleshed and dried in the field and later boiled in a 5 % aqueous solution of sodium bicarbonate to remove the remaining flesh and oil. After a rinse in fresh water, they were air-dried at room temperature for 3 to 6 months before being weighed and measured."}],"sources":[{"id":1,"label":"Fay F.H. (1982) Ecology and biology of the Pacific walrus, Odobenus rosmarus divergens Illiger. North American Fauna 74. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service. v + 279 pp.","doi":"10.3996/nafa.74.0001","url":"https://doi.org/10.3996/nafa.74.0001","type":"monograph","verified":"2026-10-30, full PDF (FWS publication, retrieved via Wayback id_ snapshot of fwspubs.org, 20161201) with text layer, checked against page renders of pp. 35–37"}],"imageRefs":[{"label":"Fay 1982, Fig. 23 (p. 37): Comparative size and shape of bacula from a Pacific walrus calf (lower) and mature adult (upper), photo by F. H. Fay, with centimetre ruler","what":"Adult baculum, lateral view with scale: silhouette, taper, distal curve, ends"}],"artNotes":"Only the bone (baculum) is shown; the soft penis was not measured and is not drawn. The outline is traced from Fay 1982 Fig. 23, with the true-size length running end to end (55.9 cm). The figure does not say which end faced the body, so we took the rough, broad end as the base.","artSimplifications":["Bone surface texture simplified","Specimen number written on the bone omitted"],"plate":{"src":{"256":"plates/walrus/256.webp","640":"plates/walrus/640.webp","1600":"plates/walrus/1600.webp","full":"plates/walrus/full.webp"},"w":2414,"h":347,"pxPerMm":4.2098,"a":[33.8,226.6],"b":[2384.1,107.8]},"portrait":{"src":{"256":"portraits/walrus/256.webp","640":"portraits/walrus/640.webp","1200":"portraits/walrus/1200.webp"},"w":2143,"h":1203,"alt":"A bull Pacific walrus, drawn side-on, tusks down.","credit":"Drawn after a photo by Bill Hickey, US Fish and Wildlife Service (Wikimedia Commons, public domain)."}},{"id":"greater-one-horned-rhinoceros","kind":"specimen","common":"Greater One-horned Rhinoceros","scientific":"Rhinoceros unicornis","group":"Mammals","tags":[],"measure":"Entire length of the fully erect penis during manual semen collection from one unsedated captive adult male (30 years old, Lincoln Park Zoo); reported as a 60–70 cm range; midpoint used","state":"erect","valueMm":650,"rangeMm":[600,700],"bodyMm":4120,"bodyMeasure":"Average head and body length (species account; sexes and n not given for this measurement)","confidence":"low","fact":"In the single rhinoceros measured erect, lateral folds 20–25 cm long opened out from the middle of the penis into cupped projections.","marginNote":"Comes with optional wings.","claims":[{"text":"Fully erect penis 60–70 cm (one male)","source":1,"locator":"p. 212","quote":"The entire length of the fully erect penis was 60-70 cm."},{"text":"Lateral folds 20–25 cm long expand into cupped projections from the middle of the penis","source":1,"locator":"p. 212","quote":"The lateral folds (20-25 cm in length) expanded into slightly cupped projections extending from the middle of the penis."},{"text":"Semi-erect penis curves backwards; it straightens on erection","source":1,"locator":"p. 212","quote":"When released from the sheath, the semi-erect penis curved caudally. Proximal to the curve were lateral, longitudinal folds."},{"text":"Straightens and swings forward on erection","source":1,"locator":"p. 212","quote":"With erection, the curve of the penis straightened, swinging the tip of the penis forward."},{"text":"Glans 13 cm long and 2.5 cm across; tip shaped like a half-bloomed bud (2 adult males, post mortem)","source":2,"locator":"p. 950","quote":"The length of the glans penis was 13 cm from the attached portion of prepuce to free extremity of the glans, and transverse diameter at the widest free part was 2.5 cm. The free extremity of the glans of rhinoceros was like a half-bloomed bud (Fig. 1)"},{"text":"Processus glandis: a lateral projection on each side of the glans","source":3,"locator":"p. 1, Diagnosis","quote":"Processus glandis of penis is located on either side of dorsum of glans, with relatively long sessile antero-posterior attachment to glans, and with long narrow projection laterally (Cave, 1964)."},{"text":"The white rhino was not used: its gross and visceral anatomy was described as virtually unknown in 1972","source":5,"locator":"p. 2","quote":"Although now frequently seen in captivity, the gross anatomy of this species, even the visceral anatomy, is virtually unknown."}],"sources":[{"id":1,"label":"Schaffer N.E., Beehler B., Jeyendran R.S., Balke B. (1990) Methods of semen collection in an ambulatory greater one-horned rhinoceros (Rhinoceros unicornis). Zoo Biology 9: 211–221","doi":"10.1002/zoo.1430090304","url":"https://rhinoresourcecenter.com/library/references/methods-of-semen-collection-in-an-ambulatory-greater-one-horned-rhinoceros-rhinoceros-unicornis/","type":"peer-reviewed","verified":"2026-10-30, full text (Rhino Resource Center PDF)"},{"id":2,"label":"Bhattacharya M., Chakraborty A., Baishya G., Dey S. (1992) Glans penis of the Indian one-horned rhinoceros (Rhinoceros unicornis). Indian Journal of Animal Sciences 62(10): 950–951","url":"https://rhinoresourcecenter.com/library/references/glans-penis-of-the-indian-one-horned-rhinoceros-rhinoceros-unicornis/","type":"peer-reviewed","verified":"2026-10-30, full text (scanned PDF from Rhino Resource Center, read from the page image)"},{"id":3,"label":"Laurie W.A., Lang E.M., Groves C.P. (1983) Rhinoceros unicornis. Mammalian Species 211: 1–6","doi":"10.2307/3504002","url":"https://rhinoresourcecenter.com/library/references/rhinoceros-unicornis/","type":"monograph","verified":"2026-10-30, full text (scanned PDF, read from the page image; no text layer)"},{"id":4,"label":"Cave A.J.E. (1964) The processus glandis in the Rhinocerotidae. Proceedings of the Zoological Society of London 143: 569–586","doi":"10.1111/j.1469-7998.1964.tb03882.x","url":"https://rhinoresourcecenter.com/library/references/the-processus-glandis-in-the-rhinocerotidae/","type":"peer-reviewed","verified":"2026-10-30, plates and legends only (the scan's text layer is unusable; body text not read)"},{"id":5,"label":"Groves C.P. (1972) Ceratotherium simum. Mammalian Species 8: 1–6","doi":"10.2307/3503966","type":"monograph","verified":"2026-10-30, full text (scanned PDF via Wayback copy of the Smith College MSI archive, read from the page image)"}],"imageRefs":[{"label":"Cave 1964, Pl. 2 fig. 1","what":"Drawing of the glans of Rhinoceros with its processus glandis: a long, narrow, lanceolate flap attached lengthwise along the side of the glans"},{"label":"Bhattacharya et al. 1992, Figs 1–2","what":"Photos of the excised glans with a ruler, showing the 'half-bloomed bud' free tip and the urethral orifice"},{"label":"Schaffer et al. 1990, Fig. 1 (supporting only)","what":"Schematic line drawing of the semi-erect penis held for semen collection, lateral; shows the caudal curve and the tip"}],"artNotes":"We found no published side view of a whole erect rhinoceros penis, so this is a composite. Overall dimensions are Schaffer's; the glans and its side projections come from Cave 1964 and Bhattacharya 1992. One lateral fold is drawn at Schaffer's mid-penis position in the shape of Cave's processus glandis. That these are the same structure, and which way the flap points, are our assumptions. Shaft width (70–75 mm) is a guess, capped by the 15 cm collection sleeve Schaffer used. No source gives the colour, so the tone is neutral. The species is the greater one-horned rhinoceros because nobody has measured a white rhinoceros penis (Groves in 1972 called its visceral anatomy 'virtually unknown'). The popular rhino figure of about 76 cm probably goes back to Nan Schaffer herself, first author of our source, who measured 60–70 cm.","artSimplifications":["Shaft girth not sourced (assumed)","Colour not sourced","Composite of whole-organ dimensions and separate glans figures"],"plate":{"src":{"256":"plates/greater-one-horned-rhinoceros/256.webp","640":"plates/greater-one-horned-rhinoceros/640.webp","1600":"plates/greater-one-horned-rhinoceros/1600.webp","full":"plates/greater-one-horned-rhinoceros/full.webp"},"w":2418,"h":340,"pxPerMm":3.6246,"a":[32,172],"b":[2388,172]},"portrait":{"src":{"256":"portraits/greater-one-horned-rhinoceros/256.webp","640":"portraits/greater-one-horned-rhinoceros/640.webp","1200":"portraits/greater-one-horned-rhinoceros/1200.webp"},"w":1911,"h":1077,"alt":"A greater one-horned rhinoceros bull, drawn side-on, in his folds of armour.","credit":"Drawn after a photo by Shadow Ayush (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"giraffe","kind":"specimen","common":"Giraffe","scientific":"Giraffa camelopardalis","group":"Mammals","tags":[],"measure":"Maximum flaccid penis length of normal adult males, quoted as a reference value in a 2020 case report that cites Hall-Martin, Skinner & Hopkins 1978 (not read). Measuring method and n unknown.","state":"flaccid","valueMm":770,"bodyMm":5500,"bodyMeasure":"Standing height (not body length), midpoint of 5–6 m; females are smaller than males","confidence":"low","fact":"The giraffe's penis is fibro-elastic and has an S-bend. At the tip is a long urethral process of the kind goats have.","marginNote":"The tip looks borrowed from a goat, though as far as anyone knows the goat has never asked for it back.","claims":[{"text":"Up to 77 cm when flaccid in normal males","source":1,"locator":"Discussion","quote":"The penis was shorter than in normal male giraffes (up to 77 cm when flaccid; Hall-Martin et al. 1978 ), situated in the perineal area and directed caudally."},{"text":"Fibro-elastic, with a sigmoid flexure and a rounded, laterally flattened glans carrying a urethral process","source":1,"locator":"Introduction","quote":"It is fibro-elastic and has a sigmoid flexure and a rounded, laterally flattened head of the penis (glans penis) with an attached urethral process."},{"text":"Long urethral process resembling a goat's","source":2,"locator":"Reproduction section","quote":"In the male, the testes are scrotal, and the penis is fibroelastic and has a long urethral process resembling that of a goat."},{"text":"Penis lies in the ventral midline and points forward","source":1,"locator":"Introduction","quote":"The penis is situated in the ventral midline and opens cranially."}],"sources":[{"id":1,"label":"Meuffels J., Luther-Binoir I., Daffue W., Deacon F., Mitchell E.P. (2020) Testicular disorder of sexual development with cryptorchidism, penile hypoplasia and hypospadias in a giraffe (Giraffa camelopardalis giraffa). Journal of the South African Veterinary Association 91: a1971","doi":"10.4102/jsava.v91i0.1971","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC7139779/","type":"peer-reviewed","verified":"2026-10-30, full text (Europe PMC XML)"},{"id":2,"label":"Aitken-Palmer C., Citino S. (2015) Giraffidae. In: Miller R.E., Fowler M.E. (eds) Fowler's Zoo and Wild Animal Medicine, Volume 8, pp. 602–610. Elsevier, St Louis","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC7151920/","type":"book","verified":"2026-10-30, full text (PMC COVID-era free chapter, Europe PMC XML)"},{"id":3,"label":"Dagg A.I. (1971) Giraffa camelopardalis. Mammalian Species 5: 1–8","doi":"10.2307/3503830","type":"monograph","verified":"2026-10-30, full text (scanned PDF via Wayback copy of the Smith College MSI archive, read from the page image)"},{"id":4,"label":"APK (2023) 'Giraffe penis.jpg': photograph of a preserved giraffe penis at the Icelandic Phallological Museum, Reykjavík. Wikimedia Commons, CC BY-SA 4.0","url":"https://commons.wikimedia.org/wiki/File:Giraffe_penis.jpg","type":"museum","verified":"2026-10-30, image viewed"}],"imageRefs":[{"label":"Icelandic Phallological Museum specimen (Wikimedia Commons, APK 2023)","what":"A preserved flaccid giraffe penis in a jar, emerging from a wrinkled preputial sleeve; the free part is a smooth cylinder with a rounded, bent tip. Unscaled and foreshortened; the urethral process is not clearly visible."}],"artNotes":"We found no scaled figure of a giraffe penis, so the proportions are assumed. The goat-like urethral process is drawn from figures of other ruminants, and the S-bend (sigmoid flexure) follows the text. The true-size length is the flaccid maximum, 'up to 77 cm', which is neither a typical nor an erect length.","artSimplifications":["Proportions assumed (no scaled figure)","Urethral process shape borrowed from ruminants","Colour unsourced","Shape of the sigmoid flexure (two opposite bends) assumed","Shaft taper (32 to 22 mm), glans (55 × 30 mm) and urethral process (40 mm) assumed, as no scaled image exists; the urethral process is counted within the 77 cm"],"plate":{"src":{"256":"plates/giraffe/256.webp","640":"plates/giraffe/640.webp","1600":"plates/giraffe/1600.webp","full":"plates/giraffe/full.webp"},"w":2415,"h":947,"pxPerMm":4.2639,"a":[40,844.1],"b":[2382.9,95.6],"path":[[40,844.1],[57.1,844.1],[74.1,844.1],[91.2,844.1],[108.3,844.1],[125.3,844.1],[142.3,844.1],[159.3,844.1],[176.4,844.1],[193.5,844.1],[210.5,844.1],[227.6,844.1],[244.7,844.1],[261.7,843.9],[278.8,842.4],[295.6,839.3],[312,834.8],[328,828.9],[343.4,821.4],[358.1,812.7],[372,802.7],[384.8,791.5],[396.7,779.1],[407.5,765.9],[417,751.5],[425.3,736.5],[432.1,720.8],[437.6,704.5],[441.5,687.8],[444,670.9],[445,653.7],[444.6,636.6],[442.5,619.6],[439,602.7],[434,586.4],[427.5,570.5],[419.7,555.1],[410.4,540.6],[400.1,527],[388.5,514.3],[375.9,502.8],[362.3,492.4],[347.9,483.4],[332.7,475.5],[316.9,469],[301.2,462.3],[286.1,454.3],[271.8,444.7],[258.5,434],[246.1,422.2],[234.9,409.4],[224.8,395.5],[216,380.8],[208.4,365.4],[202.3,349.3],[197.7,332.9],[194.4,316],[192.9,298.8],[192.6,281.7],[194,264.7],[197,247.6],[201.3,231],[207,215],[214.3,199.4],[222.8,184.5],[232.6,170.5],[243.7,157.5],[255.9,145.4],[269,134.4],[283.1,124.7],[298,116.2],[313.6,109.2],[329.7,103.6],[346.2,99.5],[363.2,96.8],[380.2,95.7],[397.3,95.6],[414.4,95.6],[431.4,95.6],[448.4,95.6],[465.4,95.6],[482.5,95.6],[499.6,95.6],[516.6,95.6],[533.7,95.6],[550.8,95.6],[567.8,95.6],[584.9,95.6],[602,95.6],[619,95.6],[636.1,95.6],[653.2,95.6],[670.2,95.6],[687.3,95.6],[704.4,95.6],[721.4,95.6],[738.5,95.6],[755.6,95.6],[772.6,95.6],[789.7,95.6],[806.8,95.6],[823.8,95.6],[840.9,95.6],[858,95.6],[874.9,95.6],[892,95.6],[909,95.6],[926.1,95.6],[943.2,95.6],[960.2,95.6],[977.3,95.6],[994.4,95.6],[1011.4,95.6],[1028.5,95.6],[1045.6,95.6],[1062.6,95.6],[1079.7,95.6],[1096.8,95.6],[1113.8,95.6],[1130.9,95.6],[1148,95.6],[1165.1,95.6],[1182.1,95.6],[1199.2,95.6],[1216.3,95.6],[1233.3,95.6],[1250.4,95.6],[1267.5,95.6],[1284.5,95.6],[1301.5,95.6],[1318.5,95.6],[1335.6,95.6],[1352.7,95.6],[1369.7,95.6],[1386.8,95.6],[1403.9,95.6],[1420.9,95.6],[1438,95.6],[1455.1,95.6],[1472.1,95.6],[1489.2,95.6],[1506.3,95.6],[1523.3,95.6],[1540.4,95.6],[1557.5,95.6],[1574.5,95.6],[1591.6,95.6],[1608.7,95.6],[1625.7,95.6],[1642.8,95.6],[1659.9,95.6],[1676.9,95.6],[1694,95.6],[1710.9,95.6],[1728,95.6],[1745.1,95.6],[1762.1,95.6],[1779.2,95.6],[1796.3,95.6],[1813.3,95.6],[1830.4,95.6],[1847.5,95.6],[1864.5,95.6],[1881.6,95.6],[1898.7,95.6],[1915.7,95.6],[1932.8,95.6],[1949.9,95.6],[1966.9,95.6],[1984,95.6],[2001.1,95.6],[2018.1,95.6],[2035.2,95.6],[2052.3,95.6],[2069.3,95.6],[2086.4,95.6],[2103.5,95.6],[2120.5,95.6],[2137.5,95.6],[2154.5,95.6],[2171.6,95.6],[2188.7,95.6],[2205.7,95.6],[2222.8,95.6],[2239.9,95.6],[2256.9,95.6],[2274,95.6],[2291.1,95.6],[2308.2,95.6],[2325.2,95.6],[2342.3,95.6],[2359.4,95.6],[2376.4,95.6],[2382.9,95.6]]},"portrait":{"src":{"256":"portraits/giraffe/256.webp","640":"portraits/giraffe/640.webp","1200":"portraits/giraffe/1200.webp"},"w":1387,"h":2091,"alt":"A bull giraffe, drawn side-on.","credit":"Drawn after a photo by Charles J. Sharp (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"domestic-bull","kind":"specimen","common":"Bull (domestic cattle)","scientific":"Bos taurus","group":"Mammals","tags":[],"measure":"Total length of the adult penis as given in a veterinary anatomy textbook (a round 'ca. 90 cm'); endpoints, measuring method and state not stated","state":"unknown","valueMm":900,"bodyMm":1502,"bodyMeasure":"Mean body length of adult (4–6 y) Lidia bulls (Spanish breed), n = 184, measured by photogrammetry, point of the shoulder to point of the buttock (trunk only; head and neck excluded, per Fig. 2, measure 20). Different population from the Sisson penis figure","confidence":"medium","fact":"A bull's penis is about 90 cm long. When it is retracted, about 30 cm of that is folded into an S-bend, which straightens out at erection.","marginNote":"Flat-packed for storage.","claims":[{"text":"Adult length about 90 cm","source":1,"locator":"p. 589","quote":"The length of the penis in the adult is about three feet (ca. 90 cm.)."},{"text":"Sigmoid flexure: about 30 cm is folded into an S-curve when retracted, and it straightens during erection","source":1,"locator":"p. 589","quote":"Just behind the scrotum it forms an S-shaped curve, the sigmoid flexure; thus about one foot of the penis is folded up when it is fully retracted. The flexure is effaced during erection."},{"text":"Fibroelastic: very little enlargement in erection, mainly increased rigidity","source":1,"locator":"p. 589","quote":"The erectile tissue is small in amount, except in the root, so that the organ undergoes very little enlargement in erection, the chief effect being increased rigidity. The walls of the cavernous spaces are fibro-elastic, not muscular."},{"text":"Dense and firm even when not erect","source":1,"locator":"p. 589","quote":"Even in the non-erect state the penis is remarkably dense and firm."},{"text":"Cylindrical, longer and much narrower than the horse's","source":1,"locator":"p. 589","quote":"The penis is cylindrical, and is longer and of very much smaller diameter than in the horse."},{"text":"Glans about 8 cm long, flattened, with a pointed, twisted tip","source":1,"locator":"p. 589","quote":"The glans penis is about three inches (ca. 8 cm.) in length. It is flattened dorso-ventrally, and its extremity is pointed and twisted. The external urethral orifice is situated at the end of a groove formed by this twist"},{"text":"Same 90 cm figure retained in the 4th edition (1953)","source":2,"locator":"p. 599","quote":"The length of the penis in the adult is about three feet (ca. 90 cm.)."},{"text":"Free part of the penis (beyond the preputial attachment) about 11 cm in 24-month-old bulls, measured post-mortem","source":3,"locator":"Discussion; Table 1","quote":"In this study, the length of the free part of the penis of Nellore bulls at 24 months of age was 11.5 cm, including the glans."},{"text":"Adult Lidia bulls (n = 184, aged 4–6 years) average 150.2 cm body length (SD 10.8; range 115.1–180.3), shoulder point to pin bone","source":4,"locator":"Materials and Methods para. 1; Table 1, row 20","quote":"The morphometry and phaneroptics data of 264 adult individuals (4–6 years) of Lidia cattle (184 males and 80 females) … 20. Body length M 150.2 a 180.3 115.1 10.8"}],"sources":[{"id":1,"label":"Sisson S. (1914) The Anatomy of the Domestic Animals. 2nd ed., entirely reset. Philadelphia & London: W. B. Saunders Company. Chapter: Genital organs of the bull, pp. 586–590; Fig. 522","url":"https://archive.org/details/cu31924001263270","type":"book","verified":"2026-10-30, full text (archive.org OCR of Cornell copy, cross-checked against page images of pp. 587–589)"},{"id":2,"label":"Sisson S., rev. Grossman J. D. (1953) The Anatomy of the Domestic Animals. 4th ed., revised. Philadelphia & London: W. B. Saunders Company","url":"https://archive.org/details/anatomyofdomesti0000sept","type":"book","verified":"2026-10-30, full-text OCR on archive.org (searched, not page images)"},{"id":3,"label":"Freitas V.M. et al. (2022) Morphological and morphometric characterization of the preputial ostium, internal preputial leaflet, and free part of the penises of Aberdeen Angus and Nellore bulls. Arq. Bras. Med. Vet. Zootec. 74(1)","doi":"10.1590/1678-4162-12419","url":"https://www.scielo.br/j/abmvz/a/XDmgswTCYTMRXQRC7xTy3FK/?lang=en","type":"peer-reviewed","verified":"2026-10-30, full text on SciELO (HTML)"},{"id":4,"label":"Lomillos J.M., Alonso M.E. (2020) Morphometric characterization of the Lidia cattle breed. Animals 10(7):1180","doi":"10.3390/ani10071180","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC7401559/","type":"peer-reviewed","verified":"2026-10-30, full text (Europe PMC full-text XML); measurement points read from Fig. 2 (saved as refs/lidia_fig2.jpg)"}],"imageRefs":[{"label":"Sisson 1914, Fig. 522 (p. 587): General view of genital organs of bull","what":"Whole penis from root to glans, lateral view, showing the sigmoid flexure (retracted), narrow distal shaft and pointed glans with external urethral orifice"}],"artNotes":"Laid out with the S-bend (sigmoid flexure) straightened, because 90 cm is the total length; the plate is not meant to show an erection. The true-size length runs from root to glans tip. Widths come from a schematic textbook drawing and are approximate.","artSimplifications":["Muscles at the root simplified","Glans twist shown schematically"],"plate":{"src":{"256":"plates/domestic-bull/256.webp","640":"plates/domestic-bull/640.webp","1600":"plates/domestic-bull/1600.webp","full":"plates/domestic-bull/full.webp"},"w":2470,"h":211,"pxPerMm":2.684,"a":[28.6,113],"b":[2444.1,113]},"portrait":{"src":{"256":"portraits/domestic-bull/256.webp","640":"portraits/domestic-bull/640.webp","1200":"portraits/domestic-bull/1200.webp"},"w":1961,"h":1261,"alt":"A black Lidia bull, drawn side-on.","credit":"Drawn after a photo by Ale823 (Wikimedia Commons, CC BY-SA 4.0)."}},{"id":"african-elephant","kind":"specimen","common":"African Bush Elephant","scientific":"Loxodonta africana","group":"Mammals","tags":["prehensile"],"measure":"Length of the erect penis of a fully grown male, given as an approximate upper value ('can reach 100 centimeters'; caption: 'Reaching about 1 meter … when erect'). Method, measurement landmarks and n not stated; species context is the African elephant photo on that page, but the anatomy chapter covers both living elephants.","state":"erect","valueMm":1000,"bodyMm":3605,"bodyMeasure":"Shoulder height of adult bulls (not body length); midpoint of 3.20–4.01 m","confidence":"low","fact":"A fully grown bull's erect penis can reach about 1 m. Its muscles probably bend it into an S, which lets him hook the tip into the cow's vulva; hers sits unusually far forward, in front of the hind legs.","marginNote":"Power steering fitted as standard.","claims":[{"text":"Erect penis of a fully grown male can reach about 1 m long, 16 cm diameter at the base","source":5,"locator":"p. 79, main text","quote":"The penis, in a fully grown male, is long, muscular and controlled by a voluntary muscle, the levator penis; it can reach 100 centimeters (3 feet 3 inches) long and has a diameter of 16 centimeters (about 6 inches) at its base."},{"text":"About 1 m and 16 cm in diameter when erect; small relative to the elephant's size","source":5,"locator":"p. 79, photo caption","quote":"Reaching about 1 meter (3 foot 3 inches), and having a diameter of about 16 centimeters (61/4 inches) when erect, the penis is small relative to the size of the elephant"},{"text":"Y-shaped urethral opening; S-shaped when fully erect","source":5,"locator":"p. 79, main text","quote":"The orifice or opening has a Y-shape. When fully erect, the penis has an S-shape."},{"text":"Y-shaped urethral opening confirmed by dissection; large unpigmented areas on the free end","source":2,"locator":"p. 528, 'Penis'","quote":"The free end of the penis and the prepuce conformed to the description given by Mojsisovics (1879) and Oudemans (1892); large areas of it are devoid of pigmentation. The opening of the urethra at the end of an ill-defined urethral process is Y shaped, the two arms of the Y being situated dorsally."},{"text":"The levator penis muscle probably causes the S-shaped bend at erection; the bull hooks the upturned tip into the vulva","source":2,"locator":"p. 531, Discussion","quote":"It is this muscle which probably accounts for the S-shaped flexure of the penis at erection, as noted by Slade (1903) and Short (1966). Presumably the male hooks the upwardly flexed tip of his penis into the ventrally situated vulva of the female"},{"text":"Proportionately very long in the African elephant, because the vulva is far forward","source":6,"locator":"Chapter on reproductive anatomy, section 'Penis' (page not visible in snippet)","quote":"The penis is proportionately very long in the African elephant, a characteristic related to the fact that, although copulation takes place a posteriori as in other ungulates"},{"text":"Large and highly muscular; the vulva is situated anterior to the hind legs","source":1,"locator":"p. 3, Form","quote":"The penis is large and highly muscular. Although copulation takes place \"a posteriori,\" the vulva of the female is situated anterior to the hind legs (Short et al., 1967)."},{"text":"Bull extends a convexly curved penis to the vulva","source":1,"locator":"p. 6, Behavior","quote":"The copulatory act commences as the bull raises his forelegs onto the cow's back and extends his convexly curved penis to the vulva."},{"text":"Well-developed corpus cavernosum and large paired levator penis muscles","source":2,"locator":"p. 517, Summary","quote":"The penis has a well-developed corpus cavernosum penis and large paired levator penis muscles on its dorsal surface."}],"sources":[{"id":1,"label":"Laursen L., Bekoff M. (1978) Loxodonta africana. Mammalian Species 92: 1–8","doi":"10.2307/3503889","type":"monograph","verified":"2026-10-30, full text (scanned PDF via Wayback copy of the Smith College MSI archive, read from the page image)"},{"id":2,"label":"Short R.V., Mann T., Hay M.F. (1967) Male reproductive organs of the African elephant, Loxodonta africana. Journal of Reproduction and Fertility 13(3): 517–536","doi":"10.1530/jrf.0.0130517","url":"https://web.archive.org/web/20200402193245id_/https://rep.bioscientifica.com/downloadpdf/journals/rep/13/3/jrf_13_3_016.pdf","type":"peer-reviewed","verified":"2026-10-30, full text read (Bioscientifica free-access PDF via Wayback Machine, capture 2020-04-02; saved as refs/short1967.pdf)"},{"id":4,"label":"Keats D. (2011) 'African Elephant, Loxodonta africana penis': photograph. Wikimedia Commons (from Flickr), CC BY 2.0","url":"https://commons.wikimedia.org/wiki/File:African_Elephant,_Loxodonta_africana_penis.jpg","type":"other","verified":"2026-10-30, image viewed"},{"id":5,"label":"Shoshani J. (1992) Anatomy and physiology. In: Shoshani J. (consulting ed.) Elephants: Majestic Creatures of the Wild. Rodale Press, Emmaus PA, p. 79 (ISBN 0875961436); reissued 2000, Checkmark Books, New York (ISBN 0816042942), same text, index 'penis 79, 80'","url":"https://archive.org/details/elephants0000unse_p3q7","type":"book","verified":"2026-10-30, read via archive.org full-text search snippets of three scans (elephants0000unse_p3q7 and elephants0000unse_y7a9 = 1992 ed., elephants00shos = 2000 ed.); overlapping snippets reassemble the sentences; page 79 from the running head adjacent to the caption and the index. Page images not viewed (lending-only). Snippets saved in refs/archive_fts_snippets.txt"},{"id":6,"label":"Sikes S.K. (1971) The Natural History of the African Elephant. Weidenfeld & Nicolson, London","url":"https://archive.org/details/naturalhistoryof0000sike","type":"monograph","verified":"2026-10-30, archive.org full-text search snippets only (lending-only); page numbers not recoverable"}],"imageRefs":[{"label":"Derek Keats 2011 photograph (Wikimedia Commons)","what":"A wild bull, lateral view of the extended but non-erect penis hanging between the legs, curving forward to a blunt tip, with pale unpigmented patches. Unscaled."}],"artNotes":"Nobody seems to have published a scaled side view of an erect elephant penis, so the S-curve and the upturned tip are drawn from written descriptions. Length and basal width follow Shoshani (1 m and 16 cm, roughly 6:1). Our only picture reference shows the organ relaxed, and we could not see the photograph on Shoshani's p. 79. The 1 m is measured along the curve.","artSimplifications":["Skin wrinkles simplified","S-curve drawn from written descriptions (the only picture reference shows the organ relaxed)","The taper (from 160 mm at the base to about 128 mm) and the exact S-curve are our assumptions","Unpigmented patches placed and sized by eye"],"plate":{"src":{"256":"plates/african-elephant/256.webp","640":"plates/african-elephant/640.webp","1600":"plates/african-elephant/1600.webp","full":"plates/african-elephant/full.webp"},"w":2418,"h":922,"pxPerMm":2.5024,"a":[74.2,271.8],"b":[2349.5,376.6],"path":[[74.2,271.8],[86.4,269.2],[98.6,266.6],[111,264.1],[123.2,261.6],[135.5,259.2],[147.7,256.8],[160.1,254.4],[172.4,252.3],[184.7,250.2],[197.1,248.1],[209.4,246.3],[221.7,244.5],[234.2,242.8],[246.6,241.3],[259,239.7],[271.5,238.3],[284,237.1],[296.3,235.9],[308.8,234.8],[321.3,233.7],[333.8,232.7],[346.3,231.9],[358.7,230.9],[371.2,230],[383.7,229.2],[396.2,228.4],[408.7,227.5],[421.1,226.7],[433.6,226],[446.1,225.4],[458.7,224.9],[471.2,224.3],[483.7,223.9],[496.1,223.7],[508.6,223.6],[521.2,223.6],[533.7,223.7],[546.2,224],[558.7,224.4],[571.2,225.1],[583.6,226],[596.1,227],[608.6,228.2],[621.1,229.6],[633.4,231.2],[645.9,233],[658.2,235],[670.6,237.2],[682.8,239.7],[695,242.4],[707.2,245.2],[719.2,248.4],[731.4,251.6],[743.3,255.3],[755.3,259.1],[767.2,263],[779,267.2],[790.6,271.6],[802.2,276.2],[813.9,281.1],[825.2,286.1],[836.6,291.3],[847.9,296.8],[859,302.4],[870.2,308.2],[881.2,314.2],[892.1,320.2],[902.9,326.5],[913.6,333],[924.2,339.6],[934.7,346.3],[945.3,353.2],[955.6,360.2],[965.9,367.3],[976.1,374.5],[986.3,381.8],[996.4,389.2],[1006.4,396.6],[1016.5,404.2],[1026.4,411.8],[1036.3,419.5],[1046.2,427.1],[1056,434.8],[1066,442.5],[1075.8,450.2],[1085.6,457.9],[1095.6,465.5],[1105.5,473.2],[1115.5,480.8],[1125.4,488.3],[1135.5,495.8],[1145.6,503.1],[1155.7,510.4],[1165.9,517.7],[1176.3,524.7],[1186.7,531.7],[1197.1,538.5],[1207.6,545.4],[1218.2,552],[1228.9,558.5],[1239.7,564.9],[1250.5,571.1],[1261.4,577.2],[1272.5,583.1],[1283.6,588.9],[1294.7,594.6],[1305.9,600.1],[1317.2,605.4],[1328.6,610.8],[1340.1,615.8],[1351.6,620.7],[1363.1,625.5],[1374.7,630.3],[1386.4,634.7],[1398,639.2],[1409.8,643.6],[1421.6,647.9],[1433.3,652],[1445.1,656.1],[1457,660.1],[1469,664],[1480.7,668],[1492.6,671.9],[1504.6,675.7],[1516.5,679.6],[1528.4,683.4],[1540.3,687.2],[1552.2,690.8],[1564.3,694.5],[1576.4,697.8],[1588.4,701.1],[1600.5,704.2],[1612.7,707],[1624.9,709.6],[1637.2,712],[1649.5,714],[1661.9,715.8],[1674.4,717.3],[1686.8,718.5],[1699.3,719.3],[1711.8,719.7],[1724.3,719.9],[1736.9,719.6],[1749.4,719],[1761.9,718],[1774.2,716.6],[1786.7,714.9],[1799,712.8],[1811.2,710.5],[1823.4,707.7],[1835.6,704.6],[1847.5,701.1],[1859.4,697.3],[1871.4,693.1],[1883,688.6],[1894.6,684],[1906,678.9],[1917.4,673.7],[1928.7,668.3],[1939.8,662.5],[1950.9,656.6],[1961.8,650.6],[1972.6,644.3],[1983.4,638],[1994.1,631.5],[2004.7,624.9],[2015.4,618.3],[2026,611.7],[2036.7,605],[2047.2,598.4],[2057.9,591.8],[2068.4,585.1],[2079,578.4],[2089.5,571.6],[2100.1,564.9],[2110.4,558],[2120.9,551.2],[2131.3,544.2],[2141.7,537.1],[2152.1,530.1],[2162.3,523],[2172.5,515.8],[2182.8,508.5],[2192.9,501.2],[2203,493.8],[2213.1,486.4],[2223,478.8],[2233,471.2],[2242.9,463.7],[2252.7,456],[2262.6,448.2],[2272.4,440.4],[2282.2,432.5],[2291.9,424.7],[2301.5,416.7],[2311.2,408.7],[2320.8,400.7],[2330.4,392.7],[2340,384.7],[2349.5,376.6],[2349.5,376.6]]},"portrait":{"src":{"256":"portraits/african-elephant/256.webp","640":"portraits/african-elephant/640.webp","1200":"portraits/african-elephant/1200.webp"},"w":2029,"h":1304,"alt":"A bull African bush elephant, drawn side-on.","credit":"Drawn after a photo by Bernard Dupont (Wikimedia Commons, CC BY-SA 2.0)."}},{"id":"blue-whale","kind":"specimen","common":"Blue Whale","scientific":"Balaenoptera musculus","group":"Mammals","tags":["record-holder"],"measure":"Penis length in fully grown Blue and Fin whales at South Georgia whaling stations; carcasses usually had the penis passively extruded after death (not an erection). Exact measuring landmarks not stated.","state":"unknown","valueMm":2250,"rangeMm":[2000,2500],"bodyMm":22600,"bodyMeasure":"Mean body length at which male Southern blue whales reach sexual maturity (same whaling-station population). This is a lower bound for fully grown males; the largest male measured was 26.45 m.","confidence":"medium","fact":"Whalers measured blue whale penises on carcasses. In life the organ stays retracted in a groove, but after death it slides out gradually during the tow back to the whaling station.","marginNote":"The whale was past caring by then.","claims":[{"text":"Usually 2 to 2.5 m long in fully grown Blue and Fin whales","source":1,"locator":"p. 380","quote":"In fully grown Blue and Fin whales the penis measures usually from 2 m. to 2-5 m., but adult specimens (e.g. No. 1229) have been recorded in which the penis measured considerably less than 2 m."},{"text":"Normally fully retracted into a groove; extrudes after death during the tow to the whaling station","source":1,"locator":"p. 380","quote":"In the male, the penis is retractile and is normally completely withdrawn into the cavity within the genital groove."},{"text":"Post-mortem extrusion during towing","source":1,"locator":"p. 380","quote":"In the carcasses of males brought to the whaling station the penis is frequently fully extruded, but this takes place gradually, after the whale has been killed, during the period when it is being towed back to the whaling station."},{"text":"A penis over about 1.5 m usually indicates a sexually mature whale","source":1,"locator":"p. 417 (Sexual maturity, males)","quote":"Among Fin whales a penis exceeding about 1-5 m. would usually indicate maturity, and about the same figure would apply to Blue whales."}],"sources":[{"id":1,"label":"Mackintosh N.A., Wheeler J.F.G. (1929) Southern Blue and Fin Whales. Discovery Reports 1: 257–540","url":"https://archive.org/details/discoveryreports01257540inst","type":"peer-reviewed","verified":"2026-10-30, full text (Internet Archive scan, BHL; OCR '2-5' = 2·5 with a raised decimal point, checked against the page image)"}],"imageRefs":[{"label":"Mackintosh & Wheeler 1929, Plate XXXIII, fig. 1","what":"Fin whale carcass on the flensing plan at a South Georgia whaling station, with the penis extruded and standing up from the ventral surface. Shows a cylindrical tapering organ with a hooked tip. Fin whale, not blue whale: the text cites this plate for penis shape in both species."}],"artNotes":"The shape comes from a photograph of a fin whale, which is in the same genus; the source lumps blue and fin whales together for length and uses one plate to show the shape of both. That organ had slid out passively after death, so this is not what an erection looks like. Proportions were read off a low-resolution halftone and are approximate.","artSimplifications":["Surface texture omitted","Shape taken from a fin whale photograph","Colour taken from a black-and-white photograph (pale tone only)"],"plate":{"src":{"256":"plates/blue-whale/256.webp","640":"plates/blue-whale/640.webp","1600":"plates/blue-whale/1600.webp","full":"plates/blue-whale/full.webp"},"w":2408,"h":838,"pxPerMm":1.1534,"a":[28.8,550.8],"b":[2233.6,84.9],"path":[[28.8,550.8],[50.4,550.8],[72.1,550.8],[93.6,550.8],[115.3,550.8],[136.9,550.8],[158.6,550.8],[180.2,550.8],[201.9,550.8],[223.4,550.8],[245.1,550.8],[266.7,550.8],[288.4,550.8],[309.9,550.8],[331.5,550.8],[353.2,550.8],[374.8,550.8],[396.5,550.8],[418,550.8],[439.7,550.8],[461.3,550.8],[483,550.8],[504.6,550.8],[526.3,550.8],[547.8,550.8],[569.4,550.8],[591.1,550.8],[612.6,550.8],[634.4,550.8],[655.9,550.8],[677.6,550.8],[699.2,550.8],[720.9,550.8],[742.4,550.8],[764.1,550.8],[785.7,550.8],[807.4,550.8],[829,550.8],[850.5,550.8],[872.2,550.8],[893.8,550.8],[915.5,550.8],[937.1,550.8],[958.8,550.8],[980.3,550.8],[1002,550.8],[1023.6,550.8],[1045.3,550.8],[1066.8,550.8],[1088.4,550.8],[1110.1,550.8],[1131.7,550.8],[1153.4,550.8],[1174.9,550.8],[1196.6,550.8],[1218.2,550.8],[1239.9,550.8],[1261.5,550.8],[1283.2,550.8],[1304.7,550.8],[1326.4,550.8],[1348,550.8],[1369.6,550.8],[1391.3,550.8],[1412.8,550.8],[1434.5,550.8],[1456.1,550.8],[1477.8,550.8],[1499.3,550.8],[1521,550.8],[1542.6,550.8],[1564.3,550.8],[1585.9,550.8],[1607.6,550.8],[1629.1,550.8],[1650.7,550.8],[1672.4,550.8],[1694,550.8],[1715.7,550.8],[1737.2,550.8],[1758.9,550.8],[1780.5,550.8],[1802.2,550.8],[1823.8,550.8],[1845.5,550.8],[1867,550.8],[1888.6,550.8],[1910.3,550.8],[1931.8,550.8],[1953.5,550.8],[1975.1,550.8],[1996.8,549.9],[2018.2,547.7],[2039.5,543.9],[2060.5,538.6],[2081.1,531.8],[2101,523.5],[2120.4,514],[2139.1,502.9],[2156.8,490.8],[2173.6,477.2],[2189.6,462.5],[2204.4,446.8],[2218,430.1],[2230.5,412.4],[2241.7,394],[2251.5,374.7],[2259.9,354.8],[2266.9,334.4],[2272.4,313.4],[2276.4,292.1],[2278.9,270.7],[2279.8,249.2],[2279.2,227.5],[2277.1,206.1],[2273.6,184.7],[2268.4,163.7],[2261.8,143.1],[2253.7,123.1],[2244.3,103.7],[2233.6,84.9],[2233.6,84.9]]},"portrait":{"src":{"256":"portraits/blue-whale/256.webp","640":"portraits/blue-whale/640.webp","1200":"portraits/blue-whale/1200.webp"},"w":2347,"h":594,"alt":"A blue whale, drawn side-on.","credit":"Drawn after a public-domain NOAA drawing (Wikimedia Commons, public domain)."}},{"id":"north-pacific-right-whale","kind":"specimen","common":"North Pacific Right Whale","scientific":"Eubalaena japonica","group":"Mammals","tags":["record-holder"],"measure":"Penis length of adult males measured on the flensing deck (Japanese special-permit catches, 1961–1962). Mean of the four adults in Table 20 (225, 215, 220, 270 cm), computed by us; the text gives the adult range 215–270 cm. Organ state at measurement not stated (dead whales, so not erect).","state":"unknown","valueMm":2325,"rangeMm":[2150,2700],"recordMm":2700,"bodyMm":16300,"bodyMeasure":"Mean body length of the same four adult males in Table 20 (17.1, 17.0, 15.1, 16.1 m), computed by us","confidence":"medium","fact":"Adult North Pacific right whales had penises of 2.15–2.7 m, and one male's two testes weighed 972 kg between them.","marginNote":"Travels heavy.","claims":[{"text":"Adult penis 215–270 cm long, 90–110 cm in girth at the base; long, slender, blue-black","source":1,"locator":"p. 35","quote":"The penis of black right whale is long and slender. It is pigmented with blue-black. As shown in Table 20, penis of adults is 215–270 cm in length, and 90–110 cm in girth at base."},{"text":"Glans nearly rectangular in cross-section","source":1,"locator":"p. 35","quote":"The cross section of glans penis is not round as those of Balaenopteridae, and it is nearly rectangle."},{"text":"Heaviest testes: 972 kg combined (Whale No. 61A); largest single testis 201 cm long and 525 kg","source":1,"locator":"p. 35","quote":"The largest one was 201 cm in length, 78 cm in diameter and 525 kg in weight. Combined weight of testes was 972 kg in the case of the heaviest (Whale No. 61A)."},{"text":"Right whales are thought to rely on sperm competition; penis length is one of the highest relative to body length among baleen whales","source":2,"locator":"p. 16 (Life cycle and reproduction)","quote":"Males have penises up to ~2.3 m long and testes with a combined weight of up to ~972 kg (Brownell and Ralls 1986; Frasier et al. 2007a)―the largest testes and highest ratio of testes to body weight of any mammal, and one of the highest ratios of penis length to body length (Brownell and Ralls 1986; Atkinson 2002; Frasier et al. 2007a)."},{"text":"Testes of right whales are the largest in the animal kingdom, about 500 kg each (genus-level statement citing Brownell & Ralls 1986)","source":3,"locator":"Ch. 23, p. 552","quote":"Sperm competition likely explains the large testis-to-body-size ratio in this genus, the largest testes in the animal kingdom weighing 500 kg each, a ton in total (Brownell and Ralls 1986)."}],"sources":[{"id":1,"label":"Omura H., Ohsumi S., Nemoto T., Nasu K., Kasuya T. (1969) Black right whales in the North Pacific. Scientific Reports of the Whales Research Institute 21: 1–78","url":"https://www.icrwhale.org/pdf/ScientificReport021.pdf","type":"peer-reviewed","verified":"2026-10-30, full text PDF from the Institute of Cetacean Research (page 35 read from page image)"},{"id":2,"label":"COSEWIC (2013) COSEWIC assessment and status report on the North Atlantic Right Whale Eubalaena glacialis in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa. xi + 58 pp.","url":"https://wildlife-species.canada.ca/species-risk-registry/virtual_sara/files/cosewic/sr_North%20Atlantic%20Right%20Whale_2013_e.pdf","type":"other","verified":"2026-10-30, full text PDF"},{"id":3,"label":"Brown M.W., Sironi M. (2023) Right whale sexual strategies and behavior. In: Würsig B., Orbach D.N. (eds) Sex in Cetaceans, pp. 543–569. Springer, Cham","doi":"10.1007/978-3-031-35651-3_23","url":"https://archive.org/details/oapen-20.500.12657-76727","type":"book","verified":"2026-10-30, full text (open-access book PDF via OAPEN/Internet Archive)"}],"imageRefs":[{"label":"Omura et al. 1969, Plate VIII, fig. 1","what":"Photo of the extruded penis of Whale No. 61A (225 cm long, 110 cm girth at insertion) on the flensing deck: thick base folded over near the genital slit, then a long narrower shaft tapering to a point"}],"artNotes":"Drawn extended, straight to gently curved, without the fold in the post-mortem photograph. The text calls the organ blue-black although the photo looks pale grey; we went with the text. The species is the North Pacific right whale because it is the only right whale with primary penis measurements. The North Atlantic figures people often quote ('up to about 2.3 m', testes 972 kg) come from Brownell & Ralls 1986, and their 972 kg testes belong to this same North Pacific whale.","artSimplifications":["Skin texture omitted","Post-mortem fold straightened"],"plate":{"src":{"256":"plates/north-pacific-right-whale/256.webp","640":"plates/north-pacific-right-whale/640.webp","1600":"plates/north-pacific-right-whale/1600.webp","full":"plates/north-pacific-right-whale/full.webp"},"w":2402,"h":432,"pxPerMm":1.0076,"a":[28,214.5],"b":[2370.6,214.5]},"portrait":{"src":{"256":"portraits/north-pacific-right-whale/256.webp","640":"portraits/north-pacific-right-whale/640.webp","1200":"portraits/north-pacific-right-whale/1200.webp"},"w":2490,"h":854,"alt":"A North Pacific right whale, drawn side-on, with the pale callosities on its head.","credit":"Drawn after a public-domain NOAA drawing (Wikimedia Commons, public domain)."}},{"id":"london-bus","kind":"reference-object","common":"London bus (New Routemaster)","scientific":"","group":"Reference objects","tags":[],"measure":"Overall vehicle length, New Routemaster (LT class) double-decker","state":"unknown","valueMm":11232,"confidence":"high","fact":"TfL's specification gives the New Routemaster as 11.232 m long, 4.42 m tall and 2.52 m wide. It has three doors and two staircases.","marginNote":"Wait twenty minutes and three of these turn up at once.","claims":[{"text":"TfL's New Routemaster specification: 11.232 m long, 4.42 m tall (unladen), 2.52 m wide excluding mirrors (2.97 m with mirrors), 12 000 kg unladen","source":1,"locator":"§2.3, p. 3","quote":"Max Height (unladen) 4420mm Width 2520mm (excluding mirrors) 2970mm (with mirrors) Length 11232mm Weight (unladen) 12000kg"},{"text":"Three doors with central and rear interconnecting staircases","source":1,"locator":"§2.1, p. 2","quote":"The NRM bus design is unique in that it has three doors with central and rear interconnecting staircases."},{"text":"Seats: 40 on the top deck, 22 on the lower deck","source":1,"locator":"§2.3, p. 3","quote":"Seating Maximum Top deck 40 - Lower deck 22"}],"sources":[{"id":1,"label":"Transport for London (2022) New Routemaster Aesthetic Mid-Life Refurbishment: Technical Requirements Specification (released under FOI request FOI-1423-2223)","url":"https://foi.tfl.gov.uk/FOI-1423-2223/New%20Routemaster%20Technical%20Specification%20FOI.pdf","type":"other","verified":"2026-10-30, full text (7-page TfL PDF)"},{"id":2,"label":"Trimming P. (2014) New Routemaster, Strand, London. Photograph, geograph.org.uk 3872429, via Wikimedia Commons, CC BY-SA 2.0","url":"https://commons.wikimedia.org/wiki/File:New_Routemaster_(geograph_3872429).jpg","type":"other","verified":"2026-10-30, image viewed"}],"imageRefs":[{"label":"Trimming, geograph 3872429 (Wikimedia Commons)","what":"Three-quarter front view: rounded front, diagonal staircase glazing, red livery, door and axle positions"}],"artNotes":"The true-size length is the body from extreme front to extreme rear (11 232 mm). Our reference photo is a three-quarter view of the side without doors, so the door side is drawn mirrored and the axles were moved to correct for perspective; door, axle, wheel and window positions are approximate. No adverts, destination blinds or roundel.","artSimplifications":["No advertising, destination blinds or text","Door and axle positions approximate (from a three-quarter photo)","Interior and passengers omitted"],"plate":{"src":{"256":"plates/london-bus/256.webp","640":"plates/london-bus/640.webp","1600":"plates/london-bus/1600.webp","full":"plates/london-bus/full.webp"},"w":2428,"h":1002,"pxPerMm":0.2108,"a":[28,498.5],"b":[2395.6,498.5]}}]