Prehistoric Life Prehistoric Secrets in Stone The Earliest Fossils The Silurian Reef Trilobites Fish The Coal Forests Early Reptiles and Amphibians Sea Reptiles Flying Reptiles The Teeming Seas Hunting Dinosaurs Biggest Dinosaurs Two-Footed Plant Eaters Plated and Armoured Dinosaurs Horned Dinosaurs The Mammal Age Dawns Grassland Mammals The Ice Age	Edmontosaurus The skeleton of the duckbill Edmontosaurus shows the gap beneath the hips. The long tail would have helped it to balance.   Previous: Back Book: Prehistoric Life Section: Prehistoric Chapter: Two-Footed Plant Eaters