Dating of the triassic period
At the beginning of the Triassic, most of the continents were concentrated in the giant C-shaped supercontinent known as Pangaea.
Climate was generally very dry over much of Pangaea with very hot summers and cold winters in the continental interior.
Late in the Triassic, seafloor spreading in the Tethys Sea led to rifting between the northern and southern portions of Pangaea, which began the separation of Pangaea into two continents, Laurasia and Gondwana, which would be completed in the Jurassic Period.
The oceans had been massively depopulated by the Permian Extinction when as many as 95 percent of extant marine genera were wiped out by high carbon dioxide levels.
This took the form of a giant "Pac-Man" with an East-facing "mouth" constituting the Tethys sea, a vast gulf that opened farther westwards in the mid-Triassic, at the expense of the shrinking Paleo-Tethys Ocean, an ocean that existed during the Paleozoic.
The Triassic Period was the first period of the Mesozoic Era and occurred between 251 million and 199 million years ago.
It followed the great mass extinction at the end of the Permian Period and was a time when life outside of the oceans began to diversify.
The extinction event that closed the Triassic period has recently been more accurately dated, but as with most older geologic periods, the rock beds that define the start and end are well identified, but the exact dates of the start and end of the period are uncertain by a few million years.
During the Triassic, both marine and continental life show an adaptive radiation beginning from the starkly impoverished biosphere that followed the Permian-Triassic extinction.