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• Basic Overview
 Animal Survivors and Newcomers
Mass extinction during the Permian Period had devastated the tetrapods (four-limbed vertebrates). Only one species out of five survived. Every tetrapod to have lived since, including you, can be traced back to these few survivors.
Mammals descended from tetrapod survivors.
One group of tetrapods, called synapsids, bounced back more quickly than did reptiles or other tetrapods. It’s lucky for you that synapids survived the extinction—mammals evolved from these survivors. If they had died out, you wouldn’t be here.
The most common synapsid fossils found from the beginning of the Triassic Period are: cynodonts (SYE-no-donts) and dicynodonts (dye-SYE-no-donts). Cynodonts had mammal-like teeth and may have had hair and whiskers—they are the synapsid group from which mammals are descended.
 From the survivors, some newcomers came—and went.
Not all extinctions are mass extinctions. New species are always evolving, but during any given time a small number are always dying out, disappearing forever.
A few tetrapods lived only during the Triassic Period. They evolved from groups that survived the extinction at the end of the Permian Period. But by the end of the Triassic, they themselves were all extinct, having left no descendants. Their fossils are the only evidence we have that they once lived.
To view more of these four-legged vertebrates that survived, thrived, and died during the Triassic Period, take a look at Tetrapod Survivor Images.
Or, continue to Mammals Materialize. >>
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