Research suggests that T rex’s eye sockets aided its bite

With a huge body, sharp claws and dagger-like teeth, Tyrannosaurus rex I wouldn’t have trusted looks to kill. But research suggests his eyes may have contributed to his bone-crushing bite.

A study has proposed that T rex’s hole-shaped eye sockets may have helped disperse stress across the fearsome predator’s skull as it chewed its prey.

“They really had specialized eye socket shapes, which helped them cope with high bite forces,” said Dr Stephan Lautenschlager, a vertebrate palaeontologist at the University of Birmingham and author of the study.

But, he added, the benefit of skull stability may have come at a cost, noting that T rex had relatively small eyes for its skull size.

While Lautenschlager said this did not mean T rex had poor eyesight, he did say that large eyes were associated with sharper vision.

“There’s a bit of a trade-off between better vision, bigger eyes, but higher stresses on the skull because of [a circular eye socket],” he said.

Writing in the journal Communications Biology, Lautenschlager analyzed the shape of the eye socket, or orbit, of 410 species that lived between 252 and 66 m years ago, including dinosaurs, pterosaurs and the ancestors of crocodiles.

Their results reveal that while most species had circular orbits, some had orbits that resembled a keyhole or a figure of eight.

“About two-thirds to three-quarters have the typical circular orbit and then the rest deviate from that and do something more extreme or more elegant,” Lautenschlager said.

Lautenschlager notes that keyhole or figure-eight orbits were commonly found among carnivores with large skulls, particularly large carnivorous theropod dinosaurs such as Tyrannosaurus rex..

“There are a few groups within theropods that have changed their diet and adapted to a herbivorous or herbivorous diet. And these again have circular orbits,” Lautenschlager said. “So [orbit shape is] very much linked to diet and size.”

Lautenschlager used a series of computer models to explore the ramifications of different eye orbit shapes, finding that a circular orbit is associated with greater deformation of the bones around the eye socket during biting, and that the hole or figure-of-eight shape of the orbits helped to distribute the stresses throughout the skull, so that they were not concentrated at one point.

The study also proposes that circular orbits could limit the space for the jaw muscles and therefore their volume, with Lautenschlager noting that this could affect the overall strength of the bite.

Lautenschlager said it was likely that non-circular eye sockets and high bite forces evolved in parallel.

“Interestingly, you see that in juvenile T rex, they still have perfectly circular or nearly circular orbits, because presumably they didn’t produce such high bite forces, or they had a slightly different diet or a different prey repertoire,” Lautenschlager added.

Professor Steve Brusatte, a palaeontologist and T rex expert at the University of Edinburgh, who was not involved in the work, welcomed the study.

“When you look at the eyes of a T rex skull, the eye socket looks kind of funny, like a keyhole. And it looks small for an animal with a head the size of a bathtub.” he said.

“This groundbreaking new study shows that T rex’s eyes were formed not only for the need for sharp vision, but also for the need to bite hard,” Brusatte said.

“Strange as it may seem, T rex’s eyes actually helped make it one of the strongest in Earth’s history.”

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