The Triassic

The Triassic began after the worst mass extinction in Earth history, at the end of the Permian. All the continents were joined in one supercontinent, Pangaea, with hot, dry interiors far from the sea.

The first dinosaurs appeared in the Late Triassic, about 230 million years ago. Early ones such as Eoraptor and Herrerasaurus from Argentina were small or medium-sized and walked on two legs. By the end of the period long-necked plant-eaters like Plateosaurus had grown much larger.

Another mass extinction closed the Triassic 201 million years ago. Many of the dinosaurs' rivals disappeared, and dinosaurs spread across the world.