Stegosauruses are some of the most iconic non-avian dinosaurs, instantly recognizable by children and adults across the world. Living around 155 to 150 million years ago, these armored herbivorous quadrupedal beasts always prove to be a boon to any museum that houses their remains.
One such specimen, nicknamed Sophie, stands in one of the entrances to London’s rather marvelous Natural History Museum (NHM). This fossil, the most intact Stegosaurus ever found, has now been the focus of a new study. Published in the journal Scientific Reports, it reveals that despite its tiny peg-shaped teeth, it had a surprisingly strong bite, one comparable to that of modern day plant-eating animals like sheep and cows.
Using cutting-edge computer simulations based on Sophie’s remarkably articulated fossilized skull, the team were able to investigate how her facial muscles would have responded to the opening and closing of her jaw. Comparing their findings to the anatomy of two other herbivorous dinosaurs, Plateosaurus and Erlikosaurus, they found that similar skull shapes don’t necessarily mean that the bite forces would also be roughly identical.
“Sophie has one of the most complete Stegosaurus skulls known,” Prof. Paul Barrett, coordinator of the research and an expert in dinosaurs and macroevolution at the NHM, told IFLScience. “This enabled us to see the bones in more detail than has been possible with any Stegosaurus skull.”
Evolutionary relationships of the studied species. Digital skull models and stress analysis models shown. Stephan Lautenschlager, University of Bristol
When Sophie lived back in the Jurassic period, she would have needed to eat a lot of plants to sustain her large size. Grasses had not yet evolved, so her diet would have presumably consisted of plants like ferns and horsetails.
Plateosaurus engelhardti and Erlikosaurus andrewsi would have had a roughly similar diet, as indicated by their comparable skull shapes. All three of these herbivorous dinosaurs had sizeable, low snouts and scissor-like jaw action that moved the teeth up and down.
However, these dinosaurs were from distally-related evolutionary lineages. While Sophie is from the Ornithischia clade, P. engelhardti is a sauropod, and E. andrewsi is a theropod. This means that although their skulls appear to have evolved to look similar – a process known as convergent evolution – it doesn’t necessarily dictate that their bite forces would be the same. Similar forms don’t always mean similar functions.
In order to solve this enigma, they turned to 3D virtual modeling. All three dinosaur skulls were digitally reproduced as computerized models, and facial muscles were then added using powerful engineering software. Data on crocodile teeth was also used to improve the accuracy of the positioning of the muscles and the movement of the jaws.
Animation showing the stresses and deformation occurring in the skull model of Stegosaurus stenops. Exaggerated 500 times. Warmer colors (yellow/red) indicate high stresses, colder colors (blue/green) indicate low stresses. Stephan Lautenschlager, University of Bristol
By looking at the most probable muscle and skeletal arrangements, the biting mechanisms of all three beasts could be calculated. As it turns out, they were all quite different: Notably, Sophie’s bite would have had the same force as a contemporary cow – far stronger than her tiny teeth initially suggested. The other two had similar bite forces, around three times less powerful than Sophie’s.
“Earlier accounts suggested that the bite force was weak, limiting Stegosaurus to soft vegetation, such as ferns, said Barrett.” This new information indicates a much stronger bite and opens up a wider range of possibilities for Stegosaurus diets, including cycads and conifer foliage. It probably had a wider dietary range, and therefore a greater ecological impact, than we thought before.”