How did tyrannosaurs eat? With really wide-hinging jaws

BRISTOL, England, Nov. 4 (UPI) -- Tyrannosaurus rex had an especially big mouth. Its powerful, wide-gaping jaw enabled T. rex's ferocious dietary habits.

In a new study, published in the journal Royal Society Open Science, researchers at the University of Bristol highlight a direct correlation between jaw size and gape and eating habits among theropod dinosaurs.

"Theropod dinosaurs, such a Tyrannosaurus rex or Allosaurus, are often depicted with widely-opened jaws, presumably to emphasize their carnivorous nature," lead study author Stephan Lautenschlager, an Earth scientist at Bristol, explained in a press release. "Yet, up to now, no studies have actually focused on the relation between jaw musculature, feeding style and the maximal possible jaw gape."

Lautenschlager and his colleagues used computer models to analyze the range of motion allowed by the jaws of three species: T. rex, a famed and fearsome meat-eating theropod; Allosaurus fragilis, a more slight of frame carnivore; and Erlikosaurus andrewsi, a sizable long-necked herbivore.

Both T. rex and A. fragilis were capable of a 90 degree jaw gape, while E. andrewsi could muster only a 45 degree opening.

The computer models also tested the strain on muscles during various jaw movements. Analysis showed only T. rex possessed the jaw musculature to enable extensive and sustained power across a wide range of jaw angles -- capable of generating bite forces strong enough to crush bone and tear through skin, muscles and ligaments.

"We know from living animals that carnivores are usually capable of larger jaw gapes than herbivores, and it is interesting to see that this also appears to be the case in theropod dinosaurs," Lautenschlager concluded.