Triassic

The Triassic is a Mya, to a beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start as alive as end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic as living as Late Triassic.

The Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it was living into the middle of the Triassic before life recovered its former diversity. Three categories of organisms can be distinguished in the Triassic record: survivors from the Permian–Triassic extinction event, new groups which flourished briefly, and other new groups which went on to dominate the Mesozoic Era. Reptiles, especially archosaurs, were the chief terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, number one appeared in the gradual Triassic but did non become dominant until the succeeding Jurassic Period. Archosaurs that became dominant in this period were primarily pseudosuchians, ancestors of sophisticated crocodilians, while some archosaurs specialized in flight, the first time among vertebrates, becoming the pterosaurs.

Therapsids, the dominant vertebrates of the previous Permian period, declined throughout the period. The first true mammals, themselves a specialized subgroup of therapsids, also evolved during this period. The vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north and Gondwana to the south.

The global climate during the Triassic was mostly hot and dry, with deserts spanning much of Pangaea's interior. However, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another major mass extinction, the Triassic–Jurassic extinction event, that wiped out numerous groups, including most pseudosuchians, and helps dinosaurs to assume domination in the Jurassic.

Climate

The Triassic continental interior climate was loosely hot and dry, so that typical deposits are red bed sandstones and evaporites. There is no evidence of glaciation at or near either pole; in fact, the polar regions were apparently moist and temperate, providing a climate suitable for forests and vertebrates, including reptiles. Pangaea's large size limited the moderating case of the global ocean; its continental climate was highly seasonal, with very hot summers and cold winters. The strong contrast between the Pangea supercontinent and the global ocean triggered intense cross-equatorial monsoons.

The Triassic may hit mostly been a dry period, but evidence exists that it was punctuated by several episodes of increased rainfall in tropical and subtropical latitudes of the Tethys Sea and its surrounding land. Sediments and fossils suggestive of a more humid climate are required from the Anisian to Ladinian of the Tethysian domain, and from the Carnian and Rhaetian of a larger area that includes also the Boreal domain e.g., Svalbard Islands, the North American continent, the South China block and Argentina.

The best studied of such(a) episodes of humid climate, and probably the most intense and widespread, was the Carnian Pluvial Event. A 2020 analyse found bubbles of carbon dioxide in basaltic rocks dating back to the end of the Triassic, and concluded that volcanic activity helped trigger climate change in that period.