History of Earth the late Paleozoic. The Mesozoic ("middle life") era lasted from 251 Ma to Ma. It is subdivided into the Triassic, Jurassic, and Cretaceous periods. The era began with the Permian–Triassic extinction event, the most severe extinction event in the fossil record; 95% of the species on Earth died out. It ended with the Cretaceous–Paleogene extinction event that wiped out the dinosaurs.. The Cenozoic ("new life") era began at Ma, and is subdivided into the Paleogene, Neogene, and Quaternary periods. These three periods are further split into seven sub-divisions, with the Paleogene composed of The Paleocene, Eocene, and Oligocene, the Neogene
Llandovery epoch Llandovery epoch In the geological timescale, the Llandovery epoch (from 443.7 ± 1.5 million years ago to 428.2 ± 2.3 million years ago) occurred during the Silurian period. The epoch follows the massive Ordovician-Silurian extinction events; the second largest extinction event after the Permian-Triassic extinction event million of years later. The epoch was named after Llandovery in Wales. The Llandovery epoch is subdivided into three stages: Rhuddanian, Aeronian and Telychian. The Lower Llandovery rocks consist of conglomerates, sandstones and slaty beds. At Llandovery they rest upon Ordovician rocks. These rocks occur with a narrow crop in Pembrokeshire, which curves round