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.