The Permian period (Permian period) is a geological period from about 299 million years ago to about 251 million years ago. However, there is an error of millions of years between the start and end times. In the past, it was often called the Nijoki from the name of the German stratum (divided into upper and lower parts), but in recent years it is often called the Permian. It is after the Carboniferous and before the Triassic. It is also the last Paleozoic period, and when the Permian period ends, it becomes the Mesozoic period. The name Permian comes from the city of Perm in Russia. The Permian is classified as the early stage (Cisuralian) up to about 273 million years ago, the middle stage (Guadalupian) up to about 259 million years ago, and the late stage (Lopingian) after that (also the start and end times). Each has an error of several million to hundreds of thousands of years).
The Permian was inhabited by various plants, giant amphibians and reptiles. Among them were dinosaurs, birds, and diapsids, the ancestors of modern reptiles. Synapsids (mammalian reptiles), the ancestors of mammals, also prospered, and a rich ecosystem was built on land. It was also around this time that the holometabol race of insects evolved. Shallow Permian marine sediments produce abundant mollusk, echinoderm, and brachiopod fossils. Trilobites were also prosperous.
As for plants, in addition to pterophyta, gymnosperms such as ginkgoales and cycads have also begun to prosper.
A close relationship has already been established between arthropods and plants.
In addition, although it is a peculiar example, the culture of microorganisms in this era has been reported. From the rock salt layer formed about 250 million years ago, we succeeded in culturing archaea and eubacteria contained inside the crystal, and the archaea are described as a new genus Halosimplex carlsbadense of the Halosimplex family. Was done.
In the early Permian period, the Euramerican continent, which existed near the equator, collided with the Gondwana continent, which had moved north from the Southern Hemisphere, forming a supercontinent called the Pangea continent. The Siberian continent existed in the northern hemisphere, but eventually the Siberian continent also collided with the Pangea continent, forming the Ural Mountains, and almost all the land was united as one supercontinent. The Pangea continent was crescent-shaped (C-shaped) across the equator. The continent was surrounded by an ocean called Pansalassa, and on the east side of the continent (inside the crescent shape), the sea called the Paleo-Tethys Ocean spread, and small continents and islands were scattered from Siberia to Gondwana. ..
In the early Permian, the climate was cold due to the Gondwana continent in Antarctica and the large ice sheet development. However, as the Gondwana continent moved north and escaped from Antarctica, the ice sheet began to melt and the temperature began to rise. At the end of the Permian, there was a sharp rise in temperature, with an average global temperature of 23 degrees Celsius. This is the highest temperature from 600 million years ago to the present. In such a climate, desertification was progressing in the inland area of Pangea.
Mass extinction at the end of the Permian (P-T boundary incident)
At the end of the Permian (P-T boundary), a mass extinction, which is said to be the largest in the history of the earth, occurred. The proportion of extinct species at this time is 96% of marine life. It is said to reach 90% to 95% of all species. The cause is still unknown, but the super plume has caused the most intense fire in Earth's history.