Os clitoridis

The os clitoridis (also called the os clitoris, clitoral bone or baubellum; pl.: baubella) is a bone inside the clitoris of many placental mammals. It is absent from the human clitoris, but present in the clitoris of some primates, such as ring-tailed lemurs and non-human great apes. However, in the latter case, the bone is greatly reduced in size. It is homologous to the baculum in male mammals.

The structure is more evolutionarily labile than the baculum, exhibiting both more inherent variability and more gains and losses over time, which has been interpreted as evidence for its non-functionality.

Other work posits that the variation in the os clitoridis could be driven by intersexual conflict, lock-and-key genital evolution, and cryptic female choice, especially given the high level of variation within species as well as between them.

The os clitoridis was described in 1666 by Claude Perrault in otters and in the lioness.

The term os clitoridis was used in 1819 by Friedrich Sigismund Leuckart regarding the capuchin monkey.

This bone was named baubellum by Guy Chester Shortridge in 1934, but it is much less common in comparison to the use of the word baculum. The Latin terms os clitoris and os clitoridis are most often found in scientific publications.

The os clitoridis has been described in species belonging to the orders Chiroptera, Primates, Rodentia and Carnivora. As with the baculum, this wide distribution suggests a primitive character that has been lost in some phylogenetic branches of the class Mammalia.

Depending on the species, the presence of this bone varies from one specimen to another. It has been observed, for example, in only 30% of American red squirrels. Its presence is even rarer in dogs: 3% (6 out of 200) presence on a radiological sample of American Cocker Spaniels and 2% (4 out of 200) for the German Shorthaired Pointer.