The Phanerozoic Eon is divided into the three eras. The oldest is the Paleozoic Era, which means ‘ancient life’ and occurred between 541 and 252 million years ago.

The Proterozoic eon was the gathering up of oxygen in Earth's atmosphere, and the Phanerozoic eon coincides with the major diversification of animals, plants, and fungi.

Often overshadowed by the more data-rich Phanerozoic Eon, this period was characterized ... by low species turnover rates. Unlike later eras, Proterozoic life was smaller, softer, and less likely ...