Dinosaur skeleton: Duckbilled dinosaurs - hadrosaurs - were plant eaters who lived in groups. This one is 66 million years old and survived a battle with a tyranosaurus rex that left a scar midway back on its tail. It probably browsed/grazed on all four legs, but it could run on its hind legs if it had to. Lower right is skeleton of a triceratops head. Denver Museum of Nature and Science, December 2005.