Tyrannosaurus rex and Velociraptor could have had their lips covering their teeth, new study suggests

An international team of paleontologists has found evidence that could change modern understanding of Tyrannosaurus rex and velociraptor.

A document published in the journal Science published on Thursday says new evidence suggests that instead of large exposed teeth, the dinosaur species actually had lips surrounding its mouth.

The discovery is an important step in uncovering a more accurate picture of creatures that lived more than 66 million years ago and could change reconstructions and depictions of dinosaurs in the future, experts in the field say. .

Derek Larson, co-author of the paper and a paleontologist at the Royal BC Museum, said dinosaur lips were not the “kissing lips” seen on mammals today. They were probably less adept and more like the lips of modern lizards.

For a long time, theropod dinosaurs such as T. rex were considered to have exposed teeth, similar to modern crocodiles, considered too large to be contained behind the lips.

Gavin Bradley, a University of Alberta paleontologist who is not involved in the article, said they were thought to have exposed teeth – similar to one of their closest living relatives, the modern crocodile.

“When we were trying to piece together the physiology or behavior of dinosaurs, we often looked at their closest living relatives, so it would be crocodiles or birds…but crocodiles don’t have lips,” he said.

This influenced popular depictions of the T. rex in artist renderings and movies, including Jurassic Park, said Thomas Cullen, lead author of the study and assistant professor at Auburn University in Alabama.

“I think that’s another piece of the puzzle of getting people to think of these animals as that, as animals and not necessarily as movie monsters,” he said.

T. rex have been portrayed as toothy predators in popular culture, like the one seen here in Jurassic Park: Fallen Kingdom, but a new study suggests otherwise. (Universal Pictures Home Entertainment)

Discover the evidence

Cullen says he started looking for evidence of theropod lips about a decade ago when he was working at the University of Toronto, alongside other paleontologists, including Larson, at the university and at the Royal Ontario Museum. It started as a side project, born out of speculation about the possibility of proving the existence of dinosaur parts – such as lips – that might have been lost over time.

“The soft tissues have all broken down, so we are left with indirect forms of evidence,” Larson said.

In their search for evidence of lips, the researchers took two approaches: examining the wear patterns of T. rex tooth enamel and comparing the proportions of its jaw and teeth to those of modern lizards.

They found that T. rex had even tooth enamel thickness, which was more consistent with constantly hydrated teeth inside a mouth than the uneven enamel of exposed crocodile teeth.

By comparing tooth and skull proportions to modern monitor lizards, the team also found that T. rex had teeth that were typically sized for a predator of its size – and some modern lizards with lips actually had larger teeth. large compared to the size of their skull.

Cullen says this evidence came around the same time in 2017 and was the first significant push that made them start to trust the lips existed.

New findings open up new avenues of study

Larson is eager to hear what Canadians and the paleontological community have to say about these discoveries.

“It’s very exciting to make discoveries like this…and finally bring them to light so that other members of the public and other scientists can see our work and evaluate it,” he said. declared.

A series of dinosaur heads, some showing teeth and some with teeth behind their lips.
Scientists and artists have developed two main patterns of predatory dinosaur facial appearances: crocodylian-like lipless jaws or lizard-like lip mouths. New data suggests that the latter pattern, lizard-like lips, applies to most or all species of predatory dinosaurs. (Mark P. Witton)

Francois Therrien, curator at the Royal Tyrrell Museum of Palaeontology in Drumheller, Alta., says the depiction of T. rex as a toothy killing machine dates back to a time when paleontologists first discovered dinosaur bones and were impressed by their frightening appearance.

However, he notes that even the skeleton of a domestic cat can look fierce on its own.

“[Cats] have big canines [and] big pointy teeth, but once you get all the flesh on the muscles and the fur on top, then there are those adorable little animals you want to play with.

“It’s not that I’m saying that basically dinosaurs would have been good pets, but they probably wouldn’t have been as scary as their bones seem to tell us,” Therrien said.

Bradley said the discovery could change reconstructions and depictions of dinosaurs in the future.

“For years we’ve always had this big picture of Tyrannosaurus rex with those steak knife teeth out in the open, showing us his toothy smile,” he said. “If people keep up to date with this research when we do these reconstructions in the media and books and things like that, you might see these teeth start to be covered.”

One of the specimens the research team used in this study was a Field-Museum-of-Natural-History T. rex nicknamed Sue, the largest T. rex ever discovered.

Canadians can view Sue’s teeth and skull at the Royal BC Museum in a traveling exhibit opening June 16.

In recent years, Therrien says research has moved from studying the genetics of dinosaurs to discerning their appearance, including the discovery that they may have been covered in feathers.

Even for the creatures that last walked the Earth millions of years ago, Cullen expects there’s still more to learn about the appearance of dinosaurs. He plans to next examine the thickness of the T. rex’s gums compared to modern lizards.

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