The hypsilophodontids were a family of dinosaurs that arose in the Middle Jurassic and are considered one of the first ornithopod groups to appear worldwide. They were a bit longer than the heterodontosaurs, averaging five feet (almost two meters) long, and some scientists compare this animal’s size and movements to today’s gazelles. They had chisel-shaped cheek teeth overlapping each other, heavy hind legs (most likely for stability when running), and a light build. They may have also nested at the same roosting place each year.

No complete skeletons have ever been found, but a recent discovery of such an animal in Texas rock layers may add new information. One fossil did show something strange: a Hypsilophodon with a broken leg that apparently healed. This could mean the animal was able to survive a severe injury; or, as some scientists speculate, it may indicate that other Hypsilophodons tended the injured member until it healed.