Science

First dinosaur butt discovered and described in (too much) detail

First dinosaur butt discovered...
An artist's recreation of Psittacosaurus and in particular, its cloacal vent
An artist's recreation of Psittacosaurus and in particular, its cloacal vent
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An artist's recreation of Psittacosaurus and in particular, its cloacal vent
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An artist's recreation of Psittacosaurus and in particular, its cloacal vent
A close up of the cloacal vent in the Psittacosaurus fossil (top) and a recreation (bottom)
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A close up of the cloacal vent in the Psittacosaurus fossil (top) and a recreation (bottom)
The exceptionally well-preserved Psittacosaurus fossil is the first to have an intact cloacal vent
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The exceptionally well-preserved Psittacosaurus fossil is the first to have an intact cloacal vent
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Paleontologists have found and described what may be the last dinosaur body part we didn’t know anything about – the butthole. Better yet, it seems like it might have evolved to look and yes, even smell, nice to suitors.

To put it a bit more scientifically, it’s a cloacal vent, a multi-purpose opening used by modern birds and reptiles to mate, lay eggs and get rid of solid and liquid waste. It’s long been presumed that dinosaurs probably had this kind of anatomy, but until now these softest of soft tissues hadn’t been well preserved.

The dinosaur finally caught with its pants down is Psittacosaurus, a Labrador-sized relative of Triceratops from the early Cretaceous, about 120 million years ago. This specimen is so well preserved that in a previous study, the team was able to see shading patterns in its skin and recreate the kind of camouflage it most likely had.

The researchers say they noticed (but politely ignored) the wardrobe malfunction at the time, but have now studied it in more detail, realizing that no one had ever described a dinosaur’s cloacal opening before. The team compared it to those of living animals, and found that it bears some resemblance to the rears of crocodiles and alligators, their closest living relatives.

The exceptionally well-preserved Psittacosaurus fossil is the first to have an intact cloacal vent
The exceptionally well-preserved Psittacosaurus fossil is the first to have an intact cloacal vent

“We found the vent does look different in many different groups of tetrapods, but in most cases it doesn’t tell you much about an animal’s sex,” says Diane Kelly, an author of the study. “Those distinguishing features are tucked inside the cloaca, and unfortunately, they’re not preserved in this fossil.”

Still, Psittacosaurus has a pretty unique butt, as far as butts go. The team noticed that the outer areas are pigmented with melanin, like the animal’s back. Since the Sun famously doesn’t shine there, they suggested that this coloration might have been used as a mating display, like a baboon’s big red behind.

A close up of the cloacal vent in the Psittacosaurus fossil (top) and a recreation (bottom)
A close up of the cloacal vent in the Psittacosaurus fossil (top) and a recreation (bottom)

The dinosaur may have made the show more interactive with the help of scent glands, which the scientists speculate were housed inside the large lobes on either side of the opening.

The discovery of the dino derriere joins a list of amazing soft tissues found in fossils, like skin, feathers, and even brains, which can teach us far more about these amazing ancient animals lived – and now, how they pooped and mated.

The research was published in the journal Current Biology.

Source: University of Bristol

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2 comments
2 comments
Bill S.
Well I don’t know about anybody else but I feel much better knowing this
Karmudjun
I now understand why some paleontologists have a little bit of the "pre-teen boy" affect. Like potty humor, discussing butts, and analyzing snot, how far a stream of pee may shoot, etc. Good to know these things, although the field may be overwhelmed with male applicants to grad school who are - shall we say - somewhat immature in some areas? I hope the current members of the field can deal with what they are creating by publicizing these breakthroughs.