How T. Rex Developed That Bone-Crushing Bite | ET REALITY

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If you have ever been in the presence of a complete fossil of a Tyrannosaurus rex, there is no doubt that it was the apex predator of its time. The adults were enormous, with giant skulls and serrated teeth the size of a banana. The force of an adult T. rex’s bite has been the subject of numerous scientific studies, but mysteries remain about what led to this powerful bite that marked the end of the age of dinosaurs.

in a investigation Published in September in the journal The Anatomical Record, a team of scientists sought to understand the oral arsenals of the tyrannosaur species that roamed the Asian and North American landscapes for millions of years before T. rex. Through their analysis of the bite forces and stress that all that swallowing puts on tyrannosaurs’ skulls, the researchers showed that tyrannosaurs steadily developed their bone-crushing powers over the eons. They also discovered that even in its juvenile form, T. rex could deliver a truly nasty bite.

It was not easy for researchers to build three-dimensional skull models of nine species of tyrannosaurs for analysis. Evan Johnson-Ransom, a University of Chicago doctoral student who led the research, said that just reconstructing digital skulls from two Asian species “took about three months since we had to work with flattened specimens.”

But the team stuck it out and eventually discovered that tyrannosaurs’ snouts conformed to two basic shapes: graceful for those that were thinner, like earlier forms of tyrannosaurs and juvenile T. rex, and then robust for heavier snouts, like that of an adult T. rex. Each three-dimensional model was then subjected to finite element analysis, a technique that determines stress and strain on biological structures. Stress, in this context, refers to the amount of force exerted on the bones of the skull, which were capable of withstanding extreme stress.

Under moderate to high stress, skulls “do a lot of biting or doing a lot of heavy lifting when feeding,” Johnson-Ransom said. Lower stress indicates that one species of tyrannosaur did not bite as hard as others.

Some of the results were expected: the larger the tyrannosaur species, the greater the bite force.

Other results were more surprising: The shape of the snout did not necessarily correlate with the stress on the skull. In fact, some early gracile-snouted tyrannosaurs had little tension in their skulls, suggesting they “didn’t bite as hard,” Johnson-Ransom said. But when a beast like the T. rex destroyed its prey with its bite, the tension in its skull was high.

Emily Rayfield, a professor of paleobiology at the University of Bristol in England, who was not involved in this study, praised the researchers for overcoming past technological limitations with their analysis. But the T. rex results surprised her.

“Their wider skulls contain more jaw-closing muscles, which means they can bite proportionately harder,” he said, “but, as a result, their skulls remain relatively stressed.”

Before reaching robustness in adulthood, a juvenile T. rex had a graceful snout. The new research highlighted how a young T. rex’s feeding capabilities allowed it to occupy a different ecological niche than it would grow into adulthood, when its skull and bite could cope with larger prey.

But even as a juvenile, the study showed, a T. rex had jaw muscle strength that could produce stronger bites than any of its non-rex tyrannosaur ancestors. This was a powerful predator regardless of its age.

Other researchers said this finding could be one of the most valuable parts of the study.

“The adult Tyrannosaurus did not exist in a vacuum,” said Thomas Holtz, a vertebrate paleontologist at the University of Maryland who was not involved in the research. “Every adult T. rex had to survive first as a baby and as a juvenile, and Tyrannosaurus itself was the product of a long evolutionary history.”

The authors hope their methods can be applied to other less-studied dinosaurs. Johnson-Ransom has already started, showing at an October meeting of the Society of Vertebrate Paleontologists what finite element analysis can tell us about spinosaurs, huge carnivores that had large sails on their backs.

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