Scientists discover how dinosaurs peed, pooped, and had sex, using an all-purpose orifice

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  • Scientists have discovered how dinosaurs peed, pooed and had sex thanks to a 130 million year old fossil.
  • The findings from the fossil found in Liaoning, China over 20 years ago were detailed in a study.
  • The paper focuses on the cloaca or posterior orifice of the Psittacosaurus dinosaur.
  • Visit Insider’s homepage for more stories.

Scientists have discovered how dinosaurs peed, pooed, and had sex for the first time, thanks to 130 million-year-old Chinese fossil.

A study published in Current Biology detailed their findings on the discovery first made in Liaoning, China, over 20 years ago.

The paper is entitled, ‘A cloacal opening in a non-avian dinosaur.’ It focuses on the cloaca or posterior orifice of the Psittacosaurus dinosaur, which lived during the Cretaceous period that began around 145 million years ago and ended around 65 million years ago.

Lead author, Dr. Jakob Vinther, a paleontologist from the University of Bristol, told Insider: “I discovered the cloaca was preserved, that we could reconstruct it and that this would be interesting in 2016.

“We realised that nobody has ever described a dinosaur cloaca before, and very few people have looked at what a cloaca and cloacal opening looks like from the outside among living animals.

“The cloaca is used for everything: peeing, pooping, laying eggs, copulation. It’s basically the Swiss army knife of orifices, it can do everything but eating and breathing,” Dr. Vinther continued.

Dinosaur
Cloaca in the fossil of the Psittacosaurus dinosaur. Dr. Jakob Vinther

With Professor Diane Kelly from the University of Massachusetts Amherst, an expert on cloaca and animal penises, and paleoartist Bob Nicholls, he created a 3D dinosaur model.

Dr. Vinther added: “The dinosaur is about the height of a Labrador, is covered in scaly skin, and has strange bristles coming off its tail. It’s a relative of some big, herbivorous dinosaurs like the Triceratops, which has horns and a frill. However, this fella has some horns on the side of its cheeks and kind of looks like ET. It’s quite cute.”


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Dr. Vinther said the sex of the dinosaur remains unknown since in animals with a cloaca, the penis is hidden inside and in this particular case, the external features don’t reveal much about that.

He added: “Dinosaurs are ancestors of birds. Birds are a group of dinosaurs that survived, so we had to look and see what they have.

“Because many groups of birds have lost their penises except for ducks, ostriches, and their relatives, birds do something called cloacal kissing where they put their cloacas together and vibrate really fast. So when birds mate, that’s typically what’s going on.”

Dinosaur
Fossil of the Psittacosaurus dinosaur. Dr. Jakob Vinther

Crocodiles are also dinosaur ancestors with penises. With that information, the scientists were able to extrapolate that if some of the deepest branches of birds in the tree of life have penises, then dinosaurs, such as the Psittacosaurus, probably have penises too.

Dr. Vinther said: “We can actually say for sure that they have a penis because the shape of this cloaca would not be particularly good for cloacal kissing. It’s a cloaca that is good for penetrative sex.”

“We could see its colour patterns, which suggests this cloaca was used for visual singling, so that means that they would been showing off their cloaca like ‘Hey, hey, check this out!’ So one of the things that we have a little glimpse into here is a glorious past where dinosaurs were engaged in cloacal signalling to attract mates,” he continued.

The Psittacosaurus fossil is currently on display at the Senckenberg Natural History Museum in Frankfurt, Germany.