|The pelycosaurs (from Greek πέλυξ pelyx "bowl" or "axe" and σαῦρος sauros "lizard") are an informal grouping (previously considered an order) composed of basal or primitive Late Paleozoic synapsid amniotes. 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. Because more advanced groups of synapsids, like therapsids evolved directly from pelycosaurs, the term had fallen out of favor among scientists by the 21st century; and is only used informally, if at all, in the modern scientific literature.
For more information, visit the Wikipedia entry
Get back to Synapsida