The weirdest
From the Hall of Fame
Corkscrews, spare heads, spines and some conspicuous absences. Under each name is the fact that got it in.
- Argentine Lake Duck Oxyura vittata: 22.3 cm
Corkscrew, Spiny. 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. - Mallard Anas platyrhynchos: 13.2 cm
Corkscrew, Spiny. 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. - Short-beaked Echidna Tachyglossus aculeatus: 7 cm
More than one head, Spiny. The glans has four rosette-tipped heads. Only two are used at once, and the left and right pairs take turns. - Chicken Gallus gallus domesticus: none
Doesn't have one. 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. - Cowpea seed beetle Callosobruchus maculatus: 0.86 mm
Spiny. 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. - Domestic Cat Felis catus: 7.5 mm
Spiny. 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. - Greater Argonaut Argonauta argo: 4.1 cm
Detachable. 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. - Pig (boar) Sus scrofa domesticus: 47.5 cm
Corkscrew. A boar's penis, 45–50 cm long, has no glans. Its front end is twisted into a spiral, usually called the corkscrew. - Red-sided Garter Snake Thamnophis sirtalis parietalis: 6.9 mm
Spiny. 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.
Also: The largest · The smallest · Largest relative to body