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	Mosasaurs In the Cretaceous period, the ichthyosaurs died out, but their place was taken by huge sea lizards called mosasaurs, such as Platycarpus. All the marine reptiles had died out by the end of the Cretaceous period. A fossil of a mosasaurus jawbone   Previous: Back Book: Prehistoric Life Section: Prehistoric Chapter: Sea Reptiles