The Hall of Ornithischian Dinosaurs examines the branches of dinosaurs that possess a backward pointing pubis bone. Additional features found within the Ornithischians include inset tooth rows forming cheeks and the uneven covering of enamel on the teeth. It is believed that both these traits allowed for increased efficiency in holding and chewing food. This hall includes such favorites as Stegosaurus, a 140-million-year-old dinosaur with distinctive rows of plates down the center of its back and large spikes in the end of its tail (along with a cast of the only juvenile Stegosaurus ever found) and the 65-million-year-old horned and shield-headed dinosaur Triceratops. This specimen has a partly healed injury on its three-horned skull, possibly caused by another Triceratops. On view nearby are the "mummy" specimens of Edmontosaurus and Corythosaurus, whose fossils have preserved large areas of skin impressions, allowing us a rare glimpse of what these creatures might have looked like alive.