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T. rex Could Open Jaw a Full 90 Degrees to Take Bite Out Of Prey, Researchers Say

Nov 04, 2015 12:58 PM EST
Life reconstruction and skull model of T-Rex showing the jaw gape at optimal position to produce muscle force and the maximal possible jaw gape. (Photo : Stephan Lautenschlager, University of Bristol)

Some carnivorous dinosaurs, such as the Tyrannosaurus rex, could open their jaws as wide as 90 degrees, say researchers from the University of Bristol who examined feeding styles and dietary preferences of dinosaurs. Digital models and computer analyses allowed researchers to closely study the muscle strain during jaw opening of three different theropod (two-legged) dinosaurs, according to to the university's news release.

"Theropod dinosaurs, such a Tyrannosaurus rex or Allosaurus, are often depicted with widely-opened jaws, presumably to emphasize their carnivorous nature," Dr. Stephan Lautenschlager, a professor in Bristol's School of Earth Sciences, explained in the release. "Yet, up to now, no studies have actually focused on the relation between jaw musculature, feeding style and the maximal possible jaw gape."

The T. rex was one of the largest land carnivores of all time. It had a massively built skull and teeth that grew up to 15 cm long. It is believed that the prehistoric animals could eat up to 500 pounds of meat in one bite. Fossil evidence also suggests that the Tyrannosaurus preyed on Triceratops and Edmontosaurus.

Allosaurus fragilis had a slightly lighter build, but was also a top meat-eating predator. For their study, researchers compared these two carnivorous theropods to their close vegetarian relative Erlikosaurus andrewsi. Using the computer models, researchers simulated the dinosaurs' jaw opening and closing and measured the length changes of their muscles. (Scroll to read more...)


(Photo : Stephan Lautenschlager, University of Bristol)
Optimal and maximal jaw gapes for the three dinosaurs in the new study: Allosaurus fragilis, Tyrannosaurus rex and Erlikosaurus andrewsi.


"All muscles, including those used for closing and opening the jaw, can only stretch a certain amount before they tear. This considerably limits how wide an animal can open its jaws and therefore how and on what it can feed," Dr. Lautenschlager added in the release.

After simulating muscle strain and maximal jaw gape in the three dinosaur species, researchers compared their data to that known of the dinosaurs' modern relatives: birds and crocodiles. 

"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," Dr. Lautenschlager said in a statement.

Overall, researchers concluded that the T. rex and Allosaurus were capable of opening their jaws up to 90 degrees, while Erlikosaurus dinosaurs could only open their jaws up to 45 degrees, according to the release.

However, T. rex bit down with greatest force for a wide range of jaw angles. This ability came in handy when the large carnivores crushed their prey and tore into their meat.

The study was recently published in the journal Royal Society Open Science.

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