Eye socket changes amped up bite force in T rex and friends

WASHINGTON: Tyrannosaurus rex possessed awe-inspiring bite force, with the huge meat-eating dinosaur’s bone-crunching chomp estimated to pack about 3,630kg of might – about equal to the weight of three small cars.

This bite strength was aided in T rex and other large predatory dinosaurs by an intriguing evolutionary modification in the skull, with the eye socket – called the orbital bone – becoming elliptical or keyhole-shaped rather than circular, according to a study published on Thursday.

The study used computer simulations to show that a skull with a circular eye socket was more vulnerable to high stresses during biting, but the modified shapes seen in large meat-eating dinosaurs greatly reduced these stresses and facilitated strong bite forces without compromising skull integrity.

“High bite forces and loads during feeding need to be accommodated by the skull and lower jaw,” said paleontologist Stephan Lautenschlager of the University of Birmingham in England, author of the research published in the journal Communications Biology.

“This can be achieved by having a stronger skull – more bone – or channeling the occurring stress and deformation in such a way that the loads are reduced. This is achieved by the non-circular orbits,” Lautenschlager added.

Lautenschlager examined eye socket shape in 410 extinct species including 230 dinosaurs as well as some of their reptilian cousins such as the crocodile lineage and the flying reptiles called pterosaurs. Of particular interest was a group called theropods, bipedal creatures that included all of the meat-eating dinosaurs.

It turned out that once a theropod species attained a skull length of about one metre or more, the shape of its eye sockets had become elliptical or keyhole-shaped.

This evolutionary change occurred independently in a variety of theropod groups globally over time, the study showed.

These included tyrannosaurs including North America’s T rex and Asia’s Tarbosaurus, carcharodontosaurs including South America’s Giganotosaurus and Africa’s Carcharodontosaurus, abelisaurs including South America’s Carnotaurus, allosaurs including North America’s Allosaurus, and spinosaurs including Africa’s Spinosaurus and Europe’s Baryonyx.