Plant-eating dinosaurs dominated the Jurassic and Cretaceous eras because they were able to make effective use of the new plant species that appeared at the time. But a new study of their secret weapon, powerful jaws, shows that their evolution was not driven by changes in the available food.
The carnivores might get the glory, but vegetarian dinosaurs outnumbered their predators hundreds to one, just as today it takes many zebras to support a single lion. It is only because the plant eaters, ornithopods in particular, were so successful at exploiting the conifers and newly emerged flowering plants that such enormous beasts could survive in large numbers. So the question of how they did this holds considerable interest.
Eddy Strickson, a Master's student at the University of Bristol said in a statement: "The plant-eating ornithopods showed four evolutionary bursts; one in the middle of the Jurassic, and the other three in a cluster around 80 million years ago in the Late Cretaceous. This was down to innovation in their jaws and improved efficiency."
Strickson is first author of a Scientific Reports paper on the changes in ornithopod jaws. Intriguingly, he found, “These evolutionary bursts do not correspond to times of plant diversification, including the radiation of the flowering plants.” It seems the ornithopods evolved their new teeth of their own accord, rather than responding to changes in the plant food on offer.