extinction

Physics & Space

Earth History & Geology

• End-Cretaceous ExtinctionAbout 66 million years ago, the Cretaceous ended in a mass extinction that eliminated all nonavian dinosaurs along with ammonites and many marine plankton groups. Roughly threequarters of species are estimated to have disappeared.
• The Great DyingThe Permian–Triassic extinction, about 251.9 million years ago, was the most severe known mass extinction. Exact percentages depend on how the fossil record is analyzed, but estimates commonly put marine species loss above 80%, with catastrophic disruption on land as well.