Triassic Period

The Triassic Period longed for 50.6 million years between 251 and 188 million years ago. It was the first period of the Mesozoic Era, and followed the great mass extinction event at the end of the Permian Period, and took place before the Jurassic period.

Until the mid-Triassic, the continents were concentrated into a vast supercontinent, called Pangea. Pangea had a form of a ginat ’C’, with the Tethys Ocean inside. The supercontinent was sorrounded by a single giant ocean, called Panthalassa. After the mid-Triassic, Pangea had begun to split into two separate parts: Laurasia (in the north, comprising Europe, Asia without India, and North America) and Gondwana (in the south, comprising Africa, South America, Antarctica, Australia, Arabia, and the Indian Subcontinent).

Triassic globe

The Earth's continents in the Triassic Period, 230 mya.

During the Triassic Period the global climate was severely hot and dry, even the poles were not covered by ice caps. Seasonal monsoons occured at coastal areas, while the isolated inside of Pangea was covered mostly with deserts. However, after Pangea started to drift apart, the climate changed to more humid.

After the Permian mass extinction event, the Triassic period was a time of diversification for the Earth’s land flora. From a low-diverse and somewhat uniform flora it became to a complex vegetation by the end of the period. Lycophythes, cycadophytes, gingkophyta, glossoptedids, ferns, then later seed ferns, bennettitales and gymnosperms were characteristics for the Triassic flora. For the late Triassic, the flora of laurasia and Gondwana showed considerable contrast, and gymnosperms became to dominant in terrestrial flora.

After the Permian extinction event ocean life was devastated and due to the high carbone dioxide levels, 95% of marine genera were wiped out. After this cataclism, marine life started to recover. However, as only a few groups managed to survive the Permian extinction, this fauna remained mostly uniform. New types of corals appeared, and formed reefs, and the ammonites, surviving the extinction with a single lineage, started to diversify again. During the Triassic some group of reptiles, like the dolphin-shaped ichthyosaurs, placodonts, the long-necked plesiosaurs and nothosaurs accommodated to marine lifestyle and returned to the oceans.

Thermospondyl amphibians were also among the survival groups of the Permian-Triassic extinction, and some of them, like capitosaurs thrieved late until the end of the Triassic Period. In the terrestrial habitats ancient reptile groups, like therapsids (also known as mammal-like reptiles) and archosaurs were the dominant vertebrates, however, most therapsids become extinct by the mid Triassic. Some important animal groups, like the first mammals and pterosaurs evolved during the Triassic. The dinosaurs, a specialized group within the archosaurs, evolved during the late Triassic.

The Triassic-Jurassic (also known as end-Triassic) extinction event, marks the end of the Triassic Period, some 201 million years ago. In the oceans about 23–34% of marine genera gone extinct. On land, many groups which were abundant during the Triassic, like most non-mammalian therapsids, many of the huge thermospondyl amphibians, most archosauromorph (except pterosaurs, dinosaurs and crocodylomorphs), were wiped out. There are gradual processes (e.g. climate change or pulse of oceanic acidification), impact of an asteroid, and massive volcanic activity amongst the possible causes of the Triassic-Jurassic extinction event.