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	Cutaway An ammonite shell was divided into separate chambers. The wall of each chamber met the outside wall in a wiggly line called the suture line. The shape of this line is useful in identifying an ammonite. The living animal occupied the last whorl (twist) of the shell.   Previous: Back Book: Prehistoric Life Section: Prehistoric Chapter: The Teeming Seas