2. History of reptiles

Abstract

‘History of reptiles’ describes the origin and early evolution of reptiles, from the early ancestor-like Hylonomus and Petrolacosaurus 320 million years ago (mya) in the Carboniferous period. The end-Permian mass extinction, 250 mya, removed over 90 per cent of the world’s species of animals and plants, but one group—the archosaurs—began to expand and diversify. The archosaurs included the dinosaurs, made up of the Theropoda, the Sauropodomorphs, the Ornithischia, the pterosaurs, and the crocodiles. In the Mesozoic Era, several new kinds of reptiles evolved adaptations for life in the sea—plesiosaurs, ichthyosaurs, and others. The end-Cretaceous mass extinction, 66 mya, ended the dinosaurs, but many lizards, snakes, chelonians, and crocodiles survived.