Iani Smithi

About 100 million years ago in what is now Utah, a 10-foot-long (3-meter-long) cousin of duck-billed dinosaurs pulverized tough plant stems and leaves with its robust teeth and powerful jaws.

It probably was too busy chewing to notice that the once-familiar world around it was transforming. But for the scientists who recently described this newfound species, its fossils offer clues about life during the middle of the Cretaceous Period (145 million to 66 million years ago), as rising air temperatures and sea levels reshaped leafy habitats on land.

The plant-eater was an early ornithopod — a group of mostly bipedal herbivorous dinosaurs. By the Cretaceous’ end, ornithopods had become the era’s most successful vegetarians, including duck-billed hadrosaurs, sometimes called “cows of the Cretaceous,” and crested Parasaurolophus, among others.