dry climate, particularly synapsids such as Dimetrodon, Edaphosaurus, and the ancestors of modern mammals. The first conifers evolved during this period, then dominated the terrestrial landscape. The Permian ended with at least one mass extinction, the Permian-Triassic mass extinction, an event sometimes known as "the Great Dying". This extinction was the largest in earth's history and led to the loss of 95% of all species of life. Mesozoic Era The Mesozoic ranges from 252 million to 66 million years ago. Also referred to as the Age of Reptiles or Age of Conifers, the Mesozoic featured the appearance of many modern tetrapods, as reptiles ascended to ecological dominance over synapsids. The Mesozoic is subdivided into three periods: the Triassic, Jurassic, and Cretaceous. Triassic Period The Triassic ranges from 252 million to 201 million years ago. The Triassic is a transitional time in Earth's history between the Permian Extinction and the lush Jurassic Period. It has three major epochs: Early Triassic, Middle Triassic. and Late Triassic. The Early Triassic lasted between 252 million to 247 million years ago, and was a hot and arid epoch in the aftermath of the Permian Extinction. Many tetrapods during this epoch represented a disaster fauna, a group of animals with low diversity and cosmopolitanism (wide geographic ranges). Temnospondyli recovered and rediversified into large aquatic predators during the Triassic. Reptiles also diversified rapidly, with aquatic reptiles such as ichthyosaurs and sauropterygians proliferating in the seas. On land, the first true archosaurs appeared, including pseudosuchians (crocodile relatives) and avemetatarsalians (bird/dinosaur relatives). The Middle Triassic spans from 247 million to 237 million years ago. The Middle Triassic featured the beginnings of the break-up of Pangaea as rifting commenced in north Pangaea. The northern part of the Tethys Ocean, the Paleotethys Ocean, had become a passive basin, but a spreading center was active in the southern part of the Tethys Ocean, the Neotethys Ocean. Phytoplankton, coral, crustaceans, and many other invertebrates recovered from the Permian extinction by the end of the Middle Triassic. Meanwhile, on land, reptiles continued to diversify, conifer forests flourished, as well as the first flies. The Late Triassic spans from 237 million to 201 million years ago. Following the bloom of the Middle Triassic, the Late Triassic was warm and arid, with a strong monsoon climate and with most precipitation limited to coastal regions and high latitudes. The first true dinosaurs appeared early in the Late