Presence in Mammals
Mammals having a penile bone (in males) and a clitoral bone (in females) include various eutherians:
- Order Primates, although not in humans or spider monkeys.
- Order Rodentia (rodents), though not in the related order Lagomorpha (rabbits, hares etc.).
- Order Insectivora (insectivores, including moles, shrews, and hedgehogs).
- Order Carnivora (including members of many well-known Families, such as Ursids (bears), Felids (cats), Canids (dogs), Pinnipeds (Walruses, Seals, Sea Lions), Procyonids (Raccoons etc.), Mustelids (Otters, weasels, skunks and others)).
- Order Chiroptera (bats).
It is absent in humans, equids, elephants, monotremes, marsupials, lagomorphs, hyenas, and cetaceans (whales, dolphins, and porpoises), among others.
Such a wide distribution among placental mammals suggests that the bone evolved early in the history of these mammals, and was subsequently lost in certain groups.
Among the primates the marmoset, weighing around 500g, has a baculum measuring around 2mm, while the tiny 63g Galago has one around 13mm long. The Great Apes, despite their size, tend to have very small penis bones, and humans are the only ones to have lost them altogether.
Read more about this topic: Baculum
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