Paleontologists make great use of teeth to identify an extinct animal's diet. Now, a study of similar theropod dinosaur teeth from the late Cretaceous has gone even further, using the way the teeth were worn down to identify differences between species.
"All these dinosaurs were living at the same time and place, so it is important to know if they were competing for food resources or if they were aiming for different prey," said Dr Angelica Torices of Universidad de La Rioja, Spain, in a statement. "Through this work we can begin to understand the interactions between these predatory dinosaurs in the ecosystem a bit better.”
With so many different carnivorous dinosaurs to study, comparing all the teeth we have is an enormous task. Torices chose to start with small- to mid-sized coelurosaurians, dinosaurs so closely related to modern birds that even their forearms were feathered. Nevertheless, they differed from modern birds in that they had teeth.
Predators have different biting strategies to get the best meal out of their prey, and some of the same approaches show up among extinct species millions of years ago as exist today. The coelurosaurian dinosaurs had blade-shaped teeth with serrated cutting edges for what is called a “puncture-and-pull” approach on their victims, adopted on a much larger scale by Tyrannosaurs rex.
However, in Current Biology, Torices has shown different families still gnawed their prey in unique ways, indicating variation in their victims. After modeling the effects on teeth from different biting approaches, Torices concluded that the teeth of troodontids were used for capturing invertebrates, small prey that could be swallowed in one bite or that were already dead. Indeed, their teeth might not have managed much more than this, experiencing high stress when used at other cutting angles.
Dromaeosaurids, on the other hand, appear to have been far more like the fearsome carnivorous dinosaurs of our nightmares, despite their small size. Their teeth carry wear consistent with holding onto large struggling prey. Like the Komodo dragon, which has similar teeth, none of the dinosaurs in the study appear to have gnawed on bone or crunched it up, instead preferring to pull the flesh away from the bone by jerking their heads back.
Tiny toothmarks, known as microwear, have been used to learn about the diets of extinct animals before, but studies of dinosaurs have focused on plant-eating species, with only passing references to patterns seen from carnivorous theropods.