New discoveries await diligent paleontologists. For proof, look no further than Jakob Vinther, a scientist at the University of Bristol in England, who recently unveiled what might be the field’s first example of a non-avian dinosaur butt.

The research, which was published in the journal Current Biology, offers a glimpse inside the backside of a psittacosaurus, a dog-sized dino whose fossilized remains managed to retain some semblance of anatomy—enough for Vinther to digitally reconstruct its, uh, butthole.

Examining the remains of the Psittacosaurus at Senckenberg Natural History Museum in Frankfurt, Germany, Vinther realized he and colleagues could develop a model for the animal’s cloaca, a multipurpose cavity that facilitates urination, bowel movements, and copulation. (Modern birds, crocodiles, and turtles are among those who sport cloacas. The word is Latin for “sewer.”) Vinther worked with co-authors like paleoartist Robert Nicholls and University of Massachusetts Amherst biologist Diane A. Kelly on the reconstruction. For reference, Kelly looked to her own collection of animal butts, as well as the active backsides of live chickens. After 120 million years, the dinosaur’s rear end was once again visible.

What secrets lurk within? For one, the cloaca appears to have a distinct color, which might have attracted potential mates. It also contains scent glands, presumably for the same purpose, and a pair of lips surrounding a dorsal lobe in the shape of a bean, an arrangement that might have resembled a drawn curtain. Naturally, Vinther also found a little bit of fossilized poop.

Beyond that, Vinther couldn’t say. If this cloaca is like a crocodile’s, it might have obscured a penis or clitoris, but no trace of any genitals was present. Patricia Brennan, an animal genitals expert at Mount Holyoke College in Massachusetts, told The New York Times that it’s possible the lobe simply expelled massive amounts of sperm in a manner similar to some bird species.

A dinosaur penis remains elusive. Only limited conclusions can be drawn from a single sample, but the cloaca is nonetheless another step in understanding the intriguing anatomy of dinosaur butts.

[h/t Popular Science]