Paleozoic era
538–252 million years ago: trilobites, giant insects and the first land animals
The Paleozoic era began about 538 million years ago with the Cambrian explosion, when most of the major animal groups appear in the fossil record within a geologically short time. It ended about 252 million years ago with the end-Permian extinction, the worst mass extinction known, which wiped out the large majority of marine species.
In between, life moved from the sea onto land. Fish grew jaws and armour, the first four-limbed animals crawled out of shallow water in the Devonian, forests of giant clubmosses covered the Carboniferous swamps, and oxygen levels high enough to support dragonflies with wingspans of around 70 cm. By the Permian, reptiles and the ancestors of mammals were the dominant animals on land.
Spin into this era and you might be a trilobite on a Cambrian reef, a Devonian fish testing the shallows, or a sail-backed Dimetrodon basking by a Permian river.
