Packed with serrated teeth larger than a banana,
the fanged maw of the Tyrannosaurus rex is iconic.
Many depictions of the prehistoric predator show its teeth protruding even when its mouth is closed, like a jagged-toothed crocodile.
However, some paleontologists believe that the T. Rex needs a good lip filler.
In a study published Thursday in Science, researchers argue that related tyrannosaurs and dinosaurs
kept their dagger-shaped teeth hidden behind lip-like tissue.
The study authors say it's time to rethink how these dinosaurs' mouths looked when they devoured their prey.
Although birds are the closest living relatives to theropod dinosaurs — the group that includes mega-predators like T. rex — their specialized beaks tell scientists little about dinosaur mouths.
For this reason, researchers often turned to crocodiles, whose exposed teeth protrude directly from the jaw without any labial tissue covering them.
Even when a crocodile's jaws are closed, its teeth are visible.
The image shared by Mark P. Witton.
This led many scientists and artists to depict lipless dinosaurs with their teeth always showing
.
One of the most influential depictions is the Tyrannosaurus from "Jurassic Park."
"That animal was copied so many times," says Mark Witton, a paleoartist and researcher at the University of Portsmouth, England, who has been illustrating lipped theropods for about a decade.
"It brought that lipless look into pop culture to the point that now we're fighting to get rid of it."
Reconstruction of a dinosaur skeleton, at the Philadelphia Museum of Natural Sciences.
Dr. Witton is one of the scientists and paleoartists who argued that theropods had a fleshy area around their mouths.
Recently, he and other colleagues teamed up to search for fossil evidence of these fuller lips.
They focused on the teeth.
According to the researchers, the teeth of many theropods were covered by a thin layer of enamel.
The researchers hypothesized that constant exposure to air could cause the enamel to become brittle and prone to chipping.
Crocodilians, for example, wear down their teeth at an accelerated rate: an American alligator can have 3,000 teeth in its lifetime.
By contrast, tyrannosaurs and other theropods used to keep their teeth much longer.
In London, an interactive exhibition on tyrannosaurus rex.
To compare wear patterns between crocodilians and theropods, the team studied thin cross sections of teeth from an American alligator and a Daspletosaurus, a close relative of T. rex.
They found that the enamel on the external, exposed face of the alligator tooth was often more eroded than that on the internal part of the tooth.
"We don't see that pattern in tyrannosaurs," said Thomas Cullen, a paleontologist at Auburn University and one of the paper's authors.
The wear on the Daspletosaurus tooth was different, a sign, they said, that a lip-like covering protected it from drying out.
The picture shows two main models of the facial appearance of predatory dinosaurs:.
"In our T-rex sample, we see a uniform thickness of enamel on both the inside and outside of the tooth, which is most similar to what we see in animals that have lips," said Dr. Cullen.
'Jurassic Park' is wrong again: the Tyrannosaurus rex had lips and no teeth were visible.
The team also examined skulls of Komodo dragons and other monitor lizards.
These reptiles have blade-shaped teeth reminiscent of those of theropods, which they keep moist under their scaly lips.
Although monitor lizards are only distantly related to theropods, the team found that the relationship between skull size and tooth size was similar.
This similarity dispels any idea that the largest carnivorous dinosaurs had trouble fitting their teeth under their lips.
But not all paleontologists are convinced by the theropod lips.
Thomas Carr, a paleontologist at Carthage College in Wisconsin, said the researchers did not take into account the bone texture of the T. rex skulls, which resembled the leathery texture of an alligator skull to the point where the teeth embed themselves in the skull. jaw.
He also argued that the dentin in tyrannosaurus teeth was more important than the enamel.
"That's the tissue that I think is structurally most important for a T-rex, because if the dentin breaks down, they're going to be eating bananas," said Dr. Carr. As a result, he thinks that keeping the enamel moist under the lips was not essential for keep teeth strong enough to bite through bone.
Dr. Witton is one of the scientists and paleoartists who argued that theropods had a fleshy area around their mouths.
The only thing that could bring the dinosaur lip debate to extinction could be a fossilized face.
"We won't have a firm answer unless we find a really rare example of a theropod with intact facial soft tissues," said Dr. Cullen.
"It's not impossible, it just hasn't happened yet."