| in Amazing Facts On Animals
The First Reptiles to Rule the Earth Were Not Dinosaurs
The earliest dinosaurs appeared some 230 million years ago, during the middle to late Triassic epoch, in the portion of the Pangean supercontinent that is now South America. Previously, archosaurs, therapsids, and pelycosaurs were the main terrestrial reptiles. Prehistoric crocodiles were the most deadly creatures on Earth for around 20 million years after dinosaurs developed. Only 200 million years ago, at the start of the Jurassic epoch, did dinosaurs actually begin their ascent to supremacy.