In many animals – and most dinosaurs – the eye sockets are circular holes in the skull housing the eyeballs. However, according to a new study led by Dr. Stephan Lautenschlager, a senior lecturer in Paleobiology at the University of Birmingham, large dinosaur predators, such as Tyrannosaurus Rex, evolved different, elliptical or oval shapes of eye sockets in order to better deal with forceful bites.
Dr. Lautenschlager analyzed the shape of the eye sockets of over 500 different dinosaurs and related species. “The results show that only some dinosaurs had eye sockets that were elliptical or keyhole-shaped,” he said. “However, all of those were large, carnivorous dinosaurs with skull lengths of one meter or more.”
By using computer simulations and stress analysis, Dr. Lautenschlager investigated what purpose such unusual eye socket shapes could have, and discovered that a skull with circular eye sockets was more prone to high stresses during biting. However, if these were replaced with elliptical or oval eye sockets, the stress during biting was considerably reduced, allowing major predators to evolve high bite sources that would not compromise their skull stability.
While most herbivorous dinosaur species and juvenile individuals retained circular eye socket shapes, large carnivores such as T. Rex adopted different morphologies, including elliptical, keyhole-shaped, of figure-of-eight-shaped sockets. “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,” explained Dr. Lautenschlager.
“These morphologies are beneficial in mitigating and dissipating feeding-induced stresses and require only little investment in reinforcing the bony structure of the skull. Conversely, the development and maintenance of large circular orbits and corresponding eyes would be physiologically costly and likely outweigh potential benefits for visual acuity,” he concluded.
The study is published in the journal Nature Communications Biology.