In the latter species, the os penis is located in the lower part of the organ and measures approximately three-quarters of an inch in length." In humans, the rigidity of the erection is provided entirely through blood pressure in the corpora cavernosa. Beach in Patterns of Sexual Behavior (1951), p. 30 say, "Both gorillas and chimpanzees possess a penile bone. Cases of human penis ossification following trauma have been reported, and one case was reported of a congenital os penis surgically removed from a 5-year-old boy, who also had other developmental abnormalities, including a cleft scrotum. In many ape species, it is a relatively insignificant 10–20 mm (0.39–0.79 in) structure. Unlike most other primates, humans lack an os penis or os clitoris, but the bone is present, although much reduced, among the great apes. If a raccoon's baculum tip is made up of uncalcified cartilage, has a porous base, is less than 1.2 g (0.042 oz) in mass, and measures less than 90 mm (3.5 in) long, then the baculum belongs to a juvenile. In some mammalian species, such as badgers and raccoons ( Procyon lotor), the baculum can be used to determine relative age. The great apes, despite their size, tend to have very small penis bones, and humans are the only ones to have lost them altogether. Īmong the primates, marmosets, weighing around 500 grams (18 oz), have a baculum measuring around 2 millimetres (0.079 in), while the tiny 63 g (2.2 oz) galago has one around 13 millimetres (0.51 in) long. The baculum is an exclusive characteristic of placentals and closely related eutherians, being absent in other mammal clades, and it has been speculated to be derived from the epipubic bones more widely spread across mammals, but notoriously absent in placentals. It is absent in humans, ungulates (hoofed mammals), elephants, monotremes ( platypus, echidna), marsupials, lagomorphs, hyenas, binturongs, sirenians, and cetaceans (whales, dolphins, and porpoises), among others.Įvidence suggests that the baculum was independently evolved 9 times and lost in 10 separate lineages. The baculum is usually longer in the Canoidea than in the Feloidea, although fossas have long bacula and giant pandas have short bacula. Order Carnivora (including members of many well-known families, such as ursids (bears), canids (dogs), pinnipeds ( walruses, seals, sea lions), procyonids (raccoons etc.), mustelids (otters, weasels, skunks and others)).Order Eulipotyphla (insectivores, including shrews and hedgehogs).
The os penis arises from primordial cells within soft tissues of the penis, and its formation is largely under the influence of androgens. It is absent from the human penis, but present in the penises of some primates, such as the gorilla and chimpanzee. The baculum (also penis bone, penile bone, or os penis, os genitale or os priapi ) is a bone found in the penis of many placental mammals. Fossil baculum of a bear ( Indarctos) from the Miocene
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