June 14, 2010
On a very superficial level, the skulls of the carnivorous theropod dinosaurs might look very much the same from species to species—big jaws filled with lots of pointy teeth. If they are examined in even a little bit of detail, however, it is quickly apparent that meat-eating dinosaurs were diverse in head shape and skull construction. Just as modern predators have different skulls suited to disparate feeding habits, the differences between one theropod skull and another may be signals of different prey preferences and feeding techniques, and in a new study paleontologist Manabu Sakamoto attempted to determine the biting function of different animals from across the spectrum of theropod diversity.
In order to test the bite forces of the 41 theropods chosen for the study, Sakamoto created virtual models using two-dimensional illustrations of their skulls and muscle attachments inferred from the anatomy of living birds and crocodiles. What the tests showed was that different kinds of theropods had significantly different types of bites. Among what are termed “high-efficiency” biters—dinosaurs that exert consistent force over the length of their jaws—were the tyrannosaurs, allosaurs and ceratosaurs. These were some of the largest and most dominant of all the theropod dinosaurs, so it was not altogether surprising that they could exert heavy pressures over most of their jaws.
On the other end of the spectrum were dinosaurs with weak, quick bites. The long-snouted, fish-eating spinosaurid dinosaurs were among those that fell into this group, as did smaller predators such as early relatives of the tyrannosaurs. In the case of the latter group, this would mean that early tyrannosaurs were capable of snapping their jaws quickly (a tactic suitable for small prey) while later tyrannosaurs were adapted to deliver strong, crushing bites. Of further interest were the small dinosaurs Coelophysis and Syntarsus. Their results were very far away from those of all other dinosaurs. This may mean that they were specialist hunters of small prey, and Sakamoto suggests that, at least in terms of bite mechanics, these dinosaurs cannot be taken as representing the ancestral condition for other groups of theropod dinosaurs.
Clearly not all theropod dinosaurs were the same. Some, such as the giants Tyrannosaurus and Carcharadontosaurus, had powerful bites that allowed them to take down and consume large prey. Dinosaurs such as the long-snouted Spinosaurus and Baryonyx, on the other hand, had jaws better suited to quickly snapping up fast-moving prey (like fish), and dinosaurs such as Coelophysis were oddballs unlike most of their theropod relatives. Likewise, as paleontologists fill out the theropod family tree with new specimens it will become possible to trace the evolution of difference biting styles in different lineages, allowing us to see how different predators became adapted to taking down and feeding on various kinds of prey.
For more on this research, see this post on Sakamoto’s blog Raptor’s Nest.
Sakamoto, M. (2010). Jaw biomechanics and the evolution of biting performance in theropod dinosaurs Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2010.0794
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