Saturday , February 27 2021

Paleontologists have finally taken a good look at dinosaur buttocks for the first time


Here is a digital reconstruction of the dinosaur Psittacosaurus, showing how a cloacal ventilator may have been used for signaling during courtship.

Bob Nicholls / 2020

Paleontologists have studied the anatomy of dinosaurs throughout their academic careers. Now, a team of scientists from the University of Bristol has finally described in detail the cloaca or dinosaur opening used for everything from excretion and urination to attracting a breeding partner (or, less scientifically, jack-of-all-butt trading).

In a new study published in the journal Current Biology on Tuesday, scientists uncovered a series of theories about cloacal venting on a large dinosaur dog named Psittacosaurus, a relative of the early Cretaceous Triceratops that lived about 120 million years ago.

“I noticed Cloaco a few years ago after we reconstructed the color patterns of this dinosaur using a remarkable fossil exhibited at the Senckenberg Museum in Germany that apparently preserves the skin and color patterns,” Dr. Jakob Vinther from the University of Bristol School. Earth Science said Tuesday.


A closer look at the preserved cloacal opening in Psittacosaurus.

Dr. Jakob Vinthe

“It took a long time before we got to finish it because no one had bothered to compare the exterior of the cloacal openings of live animals yet, so it was mostly unmarked territory,” Vinther added.

Researchers reveal that the dinosaur cloaca has similar properties to the cloaca on alligators and crocodiles. Din’s outer areas of the cloaca were probably also highly pigmented. This pigmentation may have been used to attract a partner, much like baboons use theirs.

“We’ve found that the opening looks different in different groups of tetrapods, but in most cases it doesn’t say much about the sex of the animal.” Diane Kelly of the University of Massachusetts Amherst said. “These features are embedded in the cloaca and are unfortunately not preserved in this fossil.”

Not only the appearance of the din valve is the one that caught the attention of the teammates, but also its smell. Large, pigmented lobes on either side of the cloaca could also include musky scents to attract a partner’s attention.


Psittacosaurus specimen from the Senckenberg Museum of Natural History – preserves skin and pigmentation patterns and the first and only known cloacal opening.

Jakob Vinther, University of Bristol and Bob Nicholls / 2020

“Knowing that at least some dinosaurs have signaled each other gives paleo artists an exciting freedom to speculate on a wide variety of now-likely interactions while courting dinosaurs,” said paleo artist and study artist Robert Nicholls.

“It changes the game!”

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