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	Cephalon Parts of the shell, such as the head shield (cephalon), are more common as fossils than the whole animal.   Previous: Back Book: Prehistoric Life Section: Prehistoric Chapter: Trilobites