Famously, the King of the dinosaurs, Tyrannosaurus rex had the deadliest bite of all time. An adult T. rex would have been able to bite through solid bone with a whopping 35,000 newtons of bite force compared to a human’s jaw muscles producing only 300 newtons.
According to a study published in Communications Biology, T. rex’s massive jaws may be thanks to evolving narrower eye sockets.
Stephan Lautenschlager from the UK’s University of Birmingham compared the eye sockets of 410 fossilised specimens from the time of the dinosaurs including dinosaurs themselves and their crocodilian cousins.
Most species – particularly herbivores – had circular eye sockets. Large carnivores with skulls over 1 metre like T. rex, however, often had elliptical or keyhole-shaped eye sockets. But this seems to develop over the animal’s life as juveniles tended to have more circular eye sockets.
In addition, more ancient species, including the ancestors of the large theropods like T. rex, had more circular eyes. This suggests that larger carnivores evolved narrower eye sockets over time.
To study the impact of eye socket shape, Lautenschlager used model simulations to compare the forces that a reptile skull with five different eye socket shapes was subjected to during biting.
Maximum eyeball size was also gauged. Tyrannosaurus model skulls with keyhole-shaped eye sockets deformed less during biting compared to circular sockets. Narrower eye sockets also helped reduce the stress that skulls were subjected to by distributing forces along stronger parts of the skull behind the eye socket.
Lautenschlager writes: “Biomechanical modelling using finite element analysis reveals that these morphologies are beneficial in mitigating and dissipating feeding-induced stresses without additional reinforcement of the bony structure of the skull.”
On the flip side, the model skull with a circular eye socket could accommodate an eyeball with a volume seven times larger.
Lautenschlager believes that the findings suggest that evolving narrower eye sockets may have reduced the space available for eyeballs within theropod skulls while increasing the space available for jaw muscles and enhancing the robustness of their skulls.
So, they developed a more powerful bite at the expense of larger eyes, highlighting the functional trade-offs which shaped dinosaur evolution.