- any of a group of large primitive reptiles belonging to the extinct order Pelycosauria, abundant in North America and Europe during the Permian Period, often having a tall spinal sail.
Origin of pelycosaur
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- any extinct mammal-like reptile of the order Pelycosauria, of Upper Carboniferous to Lower Permian times, from which the therapsids are thought to have evolved
C19: from New Latin Pelycosauria, from Greek pelyx bowl, pelvis, + -saur