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Dinosaur Predators Really Had Big Bite: T. rex Could Stretch Its Jaw To An Angle Of 80 Degrees

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Dinosaurs had such a remarkable jaw gape – and recent study findings in this area can leave any dinosaur lover’s mouth agape.

Researchers from the University of Bristol in England linked the feeding style and dietary choices of dinosaurs to how wide the ancient predators, particularly three theropod dinosaurs, could open their jaws. The team led by Stephan Lautenschlager used digital models and computer analyses to study the relation among jaw musculature, feeding style and the dinosaurs' maximum possible jaw gape.

The researchers found that the Tyrannosaurus rex (T. rex) and Allosaurus fragilis (Allo. fragilis), both carnivores, were able to have a wide jaw gape of up to 90 degrees.

The Allosaurus – a massive-headed, short-armed, two-legged dinosaur – opened its jaws wider than a right angle, from 79 to 92 degrees. It has a bigger jaw gape limit than the T. rex, a similar but bigger carnivore with a jaw gape of 63.5 to 80 degrees.

The findings on quick-ambush predators like the Allo. fragilis were consistent with what was required of predators who hunted larger prey, said Lautenschlager. The T. rex, in comparison, capably exerted continuous muscle force during various gape angles.

“[This] would be necessary for an animal biting through thick flesh and crushing bones,” he said.

An interesting speculation: both carnivorous theropods only rarely relied on their maximum jaw gape, such as when large prey had to be caught. The comfortable zone, according to Lautenschlager, was at the range of 28 degrees.

The herbivore Erlikosaurus andrewsi (E. andrewsi), on the other hand, had a small gape of 43.5 to 49 degrees – about half of the carnivores’. Erlikosaurus was a gawky species characterized by a long neck, convex belly and short arms, and topping out at around 20 feet long.

The herbivore’s maximum jaw gape confirmed current knowledge of living plant-eating animals having a much restricted jaw angle.

Lautenschlager said that carnivores are typically capable of bigger jaw gapes than herbivorous animals today. "[I]t is interesting to see that this also appears to be the case in theropod dinosaurs,” he confirmed.

The computer analyses in the study, published Nov. 4 in the journal Royal Society Open Science, included simulating how the dinosaurs’ jaws opened and closed and measuring changes in length in the digital muscles. The dinosaurs were also compared to their living kin, crocodiles and birds.

An understanding of jaw gape uncovered how and on what the dinosaurs can feed in the bygone era, said the researchers.

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