These familiar marine arthropods first arose about 545 million years ago in the early Cambrian and thrived throughout the world's oceans until they were wiped out in the Permian extinctions about ...

"Dinosaurs laid eggs, the fish that first crawled out of the sea laid eggs, and the weird articulated monsters that swam in the warm shallow seas of the Cambrian Period 500 million years ago also ...

dramatically. It was the time of the Cambrian Explosion, an eruption of life when Earth’s very first animals began appearing in the fossil record — the ancestors of all major animal groups ...