Tyrannosaurus rex had lips covering teeth, study finds

"Jurassic Park" may soon need a makeover.  New research suggests  Tyrannosaurus rex(T. rex) did not look like massive, upright crocodiles with sharp teeth protruding from their mouths.

Instead, lips covered the dinosaurs' teeth more similar to the lizards of today, according to the study published Thursday in the journal Science.

The teeth on T. rex and other big theropods were probably covered by scaly lips, the research suggested, adding that the teeth did not stick out when its mouth was closed.

Only the tips were visible when the giant dinosaur opened its mouth wide, researchers said.

According to Thomas Cullen, a paleontologist at Auburn University in the US state of Alabama, depictions that show big teeth jutting out of the dinosaurs' jaws are inaccurate.

Strong evidence of lip-covered teeth

The relationship between tooth size to skull size combined with the wear pattern indicated the presence of lip-like structures in the theropods group of dinosaurs, including all meat-eating  dinosaurs, the study found. 

"Our study suggests that theropod dinosaurs did not have exposed teeth when the mouth was closed," said Cullen.

"Dinosaur lips would be different from mammal lips in that they would cover the teeth but could not be moved independently — couldn't be curled back into a snarl or make other sorts of movements we associate with lips in humans or other mammals."

Instead, he added, dinosaur lips would be more similar to those of many lizards or amphibians.

Comparisons to skulls from other dinosaurs and living reptiles showed that T. rex teeth were not protruding.

Some large monitor lizards have bigger teeth than T. rex compared to their skull size and can still fit them under a set of scaly lips, Cullen said.

Analysis from Daspletosaurus tooth — a T.rex relative — found the tooth in a good condition and it didn't show an uneven damage pattern.

With this evidence and other clues from the dinosaurs' anatomy, the study makes a good case for lipped tyrannosaurs, according to University of Maryland paleontologist Thomas Holtz.

dmn/sms (Reuters, AP, AFP)