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Dinosaurs The Mammal Age Dawns Grassland Mammals The Ice Age	Petrified Wood In some fossils, the original material has been replaced by minerals from the rocks. You can still see the original structure.   Previous: Back Book: Prehistoric Life Section: Prehistoric Chapter: Secrets in Stone