Dinosaurs evolved unique eye sockets to bite harder, research shows

11 Aug 2022

The example on the right shows what a Tyrannosaurus rex would have looked like with a circular eye relative to its skull size. Image: University of Birmingham

UK researchers reveal how the unusual eye socket shapes of predators such as the T-rex could have helped the skull absorb impact as it pounced on prey.

New research indicates that predator dinosaurs evolved different eye socket shapes so they could bite harder without injury.

For many animals – including most dinosaurs – the eye socket is just a circular hole in the skull that houses the eyeball.

However, large dinosaur predators like the Tyrannosaurus rex have unusual elliptical or oval eye sockets, according to researchers in the University of Birmingham.

In the new study published today (11 August) in Communications Biology, Dr Stephan Lautenschlager analysed the eye socket shape of around 500 different dinosaurs and related species.

“The results show that only some dinosaurs had eye sockets that were elliptical or keyhole-shaped”, said Lautenschlager. “However, all of those were large, carnivorous dinosaurs with skull lengths of 1 metre or more.”

Smaller eyes, bigger bites

Using computer simulations and stress analysis, Lautenschlager found that circular eye sockets were more prone to high stresses during biting.

If these were replaced with other eye socket shapes, the stress was considerably reduced. This suggests the top dinosaur predators were able to evolve a higher bite force without compromising their skull stability.

Only large carnivores adopted these unique socket shapes such as elliptical, keyhole-shaped or figure-of-eight-shaped eye sockets.

“In these species, just the upper part of the eye socket was actually occupied by the eyeball,” Lautenschlager said. “This also led to a relative reduction of eye size compared with skull size.”

The research also showed that if eye size had increased relative to skull size, the T-rex’s eyes would have weighed 20kg, instead of the estimated weight of 2kg.

Last month, research on an ancient salamander skull shook up what scientists thought they knew about the evolution of the species. The skull was excavated from Jurassic limestones in the 1970s.

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Leigh Mc Gowran is a journalist with Silicon Republic