An article published in the journal “Royal Society Open Science” describes a research on the mouth and in particular the opening of the jaws of various dinosaurs belonging to the suborder of theropods (Theropoda). Many of them were carnivores and especially the famous ones such as the Tyrannosaurus rex or Allosaurus are generally depicted with their mouth wide open, in a menacing pose.

However, so far there had never been a study to understand how wide those animals could open their jaws. Research conducted by a team led by Dr. Stephan Lautenschlager of the University of Bristol showed a clear relationship between their diet and their maximum jaw gape.

The muscles that allow to open the jaws can stretch up to a certain point before suffering damage. This represents a limit to the opening of the mouth and consequently to what the animal could eat. Detailed computer models were created to simulate the opening and closing of the jaws of some theropod dinosaurs. The Blender free software was used to create three-dimensional models of the animals’ heads and the graphical and numberical results.

In the case of the dinosaurs, the simulations were based on the available data plausibly reproducing the movements of their mouths. They were compared to their relatives existing today, crocodiles and birds, for which data are known through direct observation.

The Tyrannosaurus rex and Allosaurus fragilis were carnivores and according to this study were able to open their mouth reaching impressive angles: 80° for the T.rex and even 92° for the Allosaurus. The study also included the Erlikosaurus andrewsi, that instead it was a herbivore theropod, whose mouth could open up to an angle that was little more than half compared to its carnivorous cousins, since it could reach 49°.

Here are some data about dinosaurs’ relatives living today. Among the crocodiles, the American alligator, or common alligator, (Alligator mississippiensis) can open its jaws until it reaches an angle of 56°. Among the birds of prey, the common buzzard (Buteo buteo) can open its jaws until it reaches an angle of 50.5°.

It’s certainly not surprising to find that carnivorous dinosaurs were able to open their mouths with big angles. This confirms the possibility of studying other species less known than the T.rex of which only partial skeletons might exist or if for other reasons there are doubts about their eating habits.