The Permian is a geologic period and system which extends from 298.9 ± 0.2 to 252.2 ± 0.5 (Million years ago). It is the last period of the Paleozoic Era, following the Carboniferous Period and preceding the Triassic Period of the Mesozoic Era. It was first introduced in 1841 by geologist Sir Roderick Murchison, and is named after the ancient kingdom of Permia. The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles, lepidosaurs and archosaurs. The world at the time was dominated by a single supercontinent known as Pangaea, surrounded by a global ocean called Panthalassa. The extensive rainforests of the Carboniferous had disappeared, leaving behind vast regions of arid desert within the continental interior. Reptiles, who could better cope with these dryer conditions, rose to dominance in lieu of their amphibian ancestors. The Permian Period (along with the Paleozoic Era) ended with the largest mass extinction in Earth's history, in which nearly 90% of marine species and 70% of terrestrial species died out. It would take well into the Triassic for life to recover from this catastrophe.
This was the period when the first group of large animals ever returned to water-the mesosaurs. The permian period was the last period of the paleozoic era and preceded the Triassic period. This was when dicynodonts and pareiasaurs were at the peak of their evolution since they were the dominant herbivores at the time and some grew up to the size of a rhino or hippo. The biggest carnivores were the pelycosaurs and gorgonopsids such as Inostrancevia alexandri. These carnivores grew up to the size of a large bear or tiger. Contrary to popular belief. Dimetrodon lived and went extinct in the Permian period and never lived alongside the dinosaurs which wouldn't be around for another 22 million years. This was also the time when the first synapsids were appearing. These were creatures with two postorbital openings. These animals would give rise to the first true mammals in the late Triassic.