The Tyrannosaurus rex was one of the top predators of the Cretaceous period. In its range , it successfully supplanted almost all other larger predatory dinosaurs, totaling probably more than 2.5 billion specimens. The T. rex also owed this to its strength and its extremely powerful bite : It could even kill large prey and crack thick bones. A special skull construction made this bite possible.
But that’s not all, as Stephan Lautenschlager from the University of Birmingham found out. Because Tyrannosaurus rex and other large predatory dinosaurs had another anatomical adaptation to their predatory way of life. For his study, the paleontologist examined how the eye shapes of different dinosaurs differ – and why. To do this, he compared the eye sockets of 410 fossil skulls from 45 different dinosaur species.
The evaluation showed that the majority of all dinosaurs had almost circular eye sockets – similar to most animals today. But there were also dinosaurs whose eye openings were conspicuously elongated and rather small. “These elliptical or bowl-hole-shaped eyes show a massive spread in the Late Cretaceous, which was mainly driven by the large theropods,” reports Lautenschlager. T. rex and the large predatory dinosaurs of its time therefore had significantly smaller eye openings than their herbivorous or smaller contemporaries.
“In these large predatory dinosaur species, the eyeball only occupied the upper part of the eye socket,” says the paleontologist. “As a result, their eyes were quite small relative to the size of their skulls.”
But why? Usually, changes in eye size are often taken as an indication of lifestyle – for example, nocturnal animals tend to have larger eyes than species that are active during the day. But in the case of T. rex and co, there was probably another reason, as biomechanical simulations suggest. In them, Lautenschlager tested the loads on the skull bones of the powerfully biting tyrannosaurus with large, round eye sockets or elongated openings.
The result: If you give the tyrannosaurus atypically large, round eye sockets, this changes the distribution of forces in the skull bones. This creates a large area of heavy stress directly behind the eyes between the cheekbone and the jawbone. “The correct skull morphology, on the other hand, interrupts this load line and leads to reduced stress loads on the skull overall,” reports Lautenschlager.
