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The most important clues as to what dinosaurs ate are provided by their teeth. Typically, the teeth of dinosaurs (like those of other reptiles) were constantly replaced from within the jaw throughout the animal’s life.

The types of food an animal eats determine the type of teeth it requires. Meat eaters need sharp, dagger-like and blade-shaped teeth for killing their prey and tearing pieces of meat from the carcass. There are, however, further differences within this group depending upon whether the prey consists of insects, fish, small mammals or large, well-defended, aggressive plant eaters or other meat eaters.

Caption: Meat-eaters: a Tyrannosaurus rex skull and its cutting teeth.

Small insect-eating dinosaurs, for example, needed only small, sharp, conical teeth that were strong enough to crunch the insects up. In contrast, large predatory dinosaurs that required lots of meat had large teeth that were powerful and sharp enough to kill their prey and then remove as much flesh as quickly as possible before other predators and scavengers were attracted to the kill. Some of these teeth had sophisticated cutting edges with serrations like those on a steak knife.

Plant-eating dinosaurs displayed an even greater variety in the form of their teeth depending upon the kind of plant material they ate. Many of the giant sauropods had strange peg-like teeth that probably worked like rakes, stripping large amounts of foliage from branches as the animal’s long neck swept from side to side and up and down. Other herbivores ate much tougher fibrous plants and had large, strong, leaf-shaped teeth that were gradually worn away and eventually replaced.

Since flowering plants did not evolve until Cretaceous times around 100 million years ago, the food available to herbivorous dinosaurs included more basic groups of plants such as ferns, conifers, cycads, horsetails and ginkgos. Many of these plants were difficult to digest and had low nutritional value. Like many herbivorous mammals today, the plant-eating dinosaurs had large stomachs and had to eat constantly to obtain enough nutrition from their diet. As an aid to digestion, some of them swallowed stones that then acted as a gastric mill along with their stomach flora of digestive bacteria. But large size slows an animal down, so how did the giant herbivores protect themselves from predators?

Caption:

Plant-eater: Iguanodon and details of its grinding teeth.