These were the Gazelles, Sheep and Rabbits of their time, and were often small and shy creatures, whose only means of survival in a world full of ravenous predators, was to use their agility and speed to escape. Most were no bigger than goats, and all were herbivores. A few were considerably larger, such as the Dryosaurus or the Parkosaurus, being over 4 metres at maximum. However, the small Ornithopod Dinosaurs were the longest lasting Herbivores – lasting from 215 million years ago, to the very end of the Age of the Dinosaurs, 65 million years ago. These animals were always in the background, behind the bigger Dinosaurs.