Dryosaurus is a small plant-eating dinosaur that lived during the late Jurassic about 150 million years ago. These dinosaurs were very successful and have been found in North America and possibly Africa. At 13 feet long and 200 pounds, these dinosaurs had little defense except speed. It is estimated that Dryosaurus could run nearly 25 miles per hour. Like other ornithopods, Dryosaurus may have lived in groups.