reword this for meh please!
The Triassic follows the largest extinction event in the history of life, and so is a time when the survivors of that event spread and recolonized.The organisms of the Triassic can be considered to belong to one of three groups: holdovers from the Permo-Triassic extinction, new groups which flourished briefly, and new groups which went on to dominate the Mesozoic world.