How can you tell from a fossil whether a dinosaur was a carnivore or a herbivore?

Just look at the animal’s mouth. “The best interpretation of a dinosaur’s diet is given by its teeth”, says paleontologist Reinaldo Bertini, from the São Paulo State University (Unesp) in Rio Claro (SP). Only carnivores’ teeth, for example, needed to be serrated, allowing them to tear the flesh of their prey.

Another important clue is the rate of change of dentition. Carnivores wore less on the arches and, therefore, fossils rarely show signs of new teeth. Those of herbivores, on the other hand, were changed more often because they suffered greater wear and tear – due to the repetitive maceration of the plants inside the mouth.

Most of the dinosaurs that inhabited Earth until the end of the Cretaceous period, 65 million years ago, had a vegetarian diet – the ratio was nine herbivores for each carnivore. There was still a third category, the omnivores, who, like man, ate both meat and vegetables. But those were even rarer.

The food preference was directly related to the animal’s behavior and its locomotion capacity. Carnivores were more agile, since, in order to get food, they needed to attack quickly. But the terrible tyrannosaurus, despite its reputation as evil, was a scavenger, that is, it fed mainly on animals that were already dead. This prehistoric scavenger had teeth that could reach eight inches, the largest among carnivores. The big herbivores, on the other hand, were more docile and slower. Their slowness, of course, made them easy prey for flesh eaters.