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	Boneheads Another group of plant eaters with strange skulls was the boneheads, such as Stygimoloch. These were two-footed plant eaters, but they had thick bony heads that must have been used as battering rams.   Previous: Back Book: Prehistoric Life Section: Prehistoric Chapter: Horned Dinosaurs