Pelycosaurs were the earliest of the synapsid, or mammal-like, reptiles to evolve. They appeared during the Late Carboniferous period, some 300 million years ago, soon after the very first reptiles colonized the land (see pp. 62-65).

When did pelycosaurs appear?

Evolutionary history

The pelycosaurs appeared during the Late Carboniferous and reached their apex in the early part of the Permian, remaining the dominant land animals for some 40 million years.

When did Pelycosaur go extinct?

Dimetrodon, an extinct relative of primitive mammals, lived from about 286 million to 270 million years ago, during the Permian Period, in the section of Pangea that would eventually split off to become North America.