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	Pygidium Shell pieces, such as the tail shield (pygidium), were shed many times during the trilobite's life, so one trilobite could produce many fossils.   Previous: Back Book: Prehistoric Life Section: Prehistoric Chapter: Trilobites