Walking With Wikis
Carboniferous - Permian

Dimetrodon eating.jpg


The pelycosaurs (from Greek πηλυξ, pelyx meaning 'bowl' and σαυρος, sauros meaning 'lizard') were primitive Late Paleozoic synapsids. Some species were quite large and could grow up to 3 meters or more, although most species were much smaller. It must be remembered, however, that the pelycosaurs are now considered to be an informal grouping of synapsids, in part because the more advanced synapsids (i.e. therapsids) have evolved directly from pelycosaurs instead.


The pelycosaurs appeared during the Late Carboniferous and reached their acme in the early part of the Permian period, remaining the dominant land animals for some 40 million years. A few continued into the late Permian. They were succeeded by their descendants, the therapsids, which had a short but successful reign before the Permian–Triassic extinction event, giving a chance for the archosaur reptiles to take over in the Triassic.

Pelycosaurs were among the most ancient of the mammal-like reptiles. However, they already had some of mammal-like characteristics, such as different kinds of teeth in their mouth. They would be eventually replaced by therapsids and similar creatures.

In Walking with... Series

Walking with Monsters

Reptile's Beginnings

This episode featured two of the better-known pelycosaurs: Dimetrodon and Edaphosaurus. Although they were superficially similar to each other, they were only distant relatives. Both of them had sails, supposedly to help them warm up and cool down, or to be used when courting the females. Dimetrodon was shown to be the main predator of the Permian, while Edaphosaurus was among the first reptiles to eat plants instead of meat. By the late Permian, they became replaced by therapsids and pareiasaurs, respectively.