It lasted a long time, nearly 80 million years, making it the longest geological period of the Phanerozoic Eon, which began some 539 million years ago. The Cretaceous is split into two smaller time ...

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 critical evolutionary, environmental, and tectonic changes. However, the fossil record of Proterozoic ...