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Female snakes have not one, but two clitorises, according to research documenting the first formal evidence of the sexual organ in snakes. This two-part clitoris, called a hemiclitoris, is present in at least nine snake species.

“There’s a lot known about male snake genitalia, but not so much – really anything – known about females,” says at the University of Adelaide in Australia. Previous research was “kind of all over the place about whether the snake clitoris existed”. Wanting to settle the debate, Folwell and her colleagues began dissecting female snake specimens from the University of Michigan’s zoology collection.

Folwell says it didn’t take much searching. “You peel back the skin and it’s right there in front of you,” she says. They found hemiclitores in all nine species they looked at, and all were located on the underside of the snake’s tail.

Dissections and micro-CT scans revealed a range of hemiclitoris sizes and structures between species. The cantil viper (Agkistrodon bilineatus), a pit viper native to Mexico, has the largest hemiclitoris of the nine species, while an Australian species, Ingram’s brown snake (Pseudonaja ingrami), has the smallest. Other species they examined included the common death adder (Acanthophis antarcticus), Guatemalan milk snake (Lampropeltis abnorma) and carpet python (Morelia spilota). Folwell says she suspects most, if not all, female snake species have hemiclitores.

The team also found that, like male snakes’ and lizards’ two-part hemipenes, females’ hemiclitores are comprised of sensitive nerves and erectile tissue. But unlike hemipenes, the females’ hemiclitores lack spines and hooks thought to assist in mating.

The work “provides indisputable evidence that [the clitoris] is there, and it’s large, and it’s complex”, says at Macquarie University in Australia who was not involved in the work. “It’s a great leap forward in our understanding of sexual anatomy in reptiles.”

When it comes to studying animal genitalia, “I think female side of things get a little bit lost,” says Folwell. “But there’s now a brilliant community of scientists looking into female genitalia, which is really exciting stuff.”

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