The Triassic was the time of Pangea.
The continental crust formed one large land mass, shaped like a sideways
v, with the Tethys ocean inside. The redbeds in the rock record; for which
the triassic is known, indicate that their depositional environment was
mainly a terrestrial one, in a semiarid to monsoonal, warm to hot climate.
During the Triassic Pangea stood at its highest elevation with a generally warm climate, and the ice caps of the Gondwana region were gone. The triassic saw a mixture of fauna that survived fro the paleozoic, such as Cotylosaurs, which would indicate the shape of life forms to come. The Triassic also saw the appearance of the first dinosaurs.
During the triassic organisms that were adapted to life on land first returned to the sea. By the end of the triassic the Icthyosaurs, the most fish like of the marine reptiles, were one of the dominant marine predators.
Placodonts were among the reptiles that adapted to marine life, but unlike Icthyosaurs Placodonts were adapted to life on the shallows. Another reptilian group that appeared during the triassic were the Nothosaurs, which eventually evolved into the plesiosaurs.
The Triassic ended with a mass extinction
and Pangea began to break up, this resulted in a marine transgression,
Due to the reduction of volume of the worlds ocean basins. The jurassic
moslty saw a radiation of organisms that continued through the cretaceous.