Large predatory dinosaurs, such as the T. rex, evolved different eye socket shapes to allow for stronger bites.

According to new research, large predatory dinosaurs such as Tyrannosaurus Rex Various forms of eye cavities have been developed to better handle higher biting forces.

Whereas in many animals, including most dinosaurs, the eye socket is just a circular hole in the skull that contains the eyeball, this is quite different in larger carnivores.

A new study has revealed how the unusual oval or oval eye sockets found in the skulls of these predators may have evolved to help the skull absorb shock when it pounces on prey. This research by scientists in University of Birminghampublished today (August 11, 2022) in Communication Biology.

Skull and life reconstructions in Tyrannosaurus Rex with the original eye socket and eye (left) and virtual reconstruction using a circular eye socket and enlarged eye (right). Credit: Dr. Stefan Lautschlager, University of Birmingham

Dr. Stefan Luttenschlager, Senior Lecturer in Paleobiology at[{” attribute=””>University of Birmingham and author of the new study, analyzed the shape of the eye sockets of ca. 500 different dinosaurs and related species.

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

Computer simulations of hypothetical dinosaur skulls. Colors indicate skull stress. High stresses occur in the skull with a round eye socket (top), lower stresses in a skull with a keyhole-shaped eye socket (bottom). Credit: Dr. Stephan Lautenschlager, University of Birmingham

Dr. Lautenschlager tested what purpose these unusual eye socket shapes could have by using computer simulations and stress analysis.

The results demonstrated that a skull with a circular eye socket was more prone to high stresses during biting. However, if these were replaced with other eye socket shapes stresses were significantly reduced. This allowed top predators, including Tyrannosaurus rex, to evolve high bite forces without compromising skull stability.

The study also showed that most plant-eating species and juvenile individuals retained a circular eye socket. Only large carnivores adopted other morphologies, such as elliptical, keyhole-shaped, or figure-of-eight-shaped eye sockets.

Skulls of different dinosaurs showing variation in eye socket shape (stippled outline). Credit: Dr. Stephan Lautenschlager, University of Birmingham

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

The researchers also investigated what would have happened if eye size had increased at the same rate as skull length. In such a case, the eyes of Tyrannosaurus rex would have been up to 30 cm (12 inches) in diameter and weighed nearly 20 kg (44 pounds). This is instead of an estimated 13 cm (5 inches) and 2 kg (4.4 pounds).

Reference: “Functional and ecomorphological evolution of orbit shape in mesozoic archosaurs is driven by body size and diet” by Stephan Lautenschlager, 11 August 2022, Communications Biology.
DOI: 10.1038/s42003-022-03706-0