that is as wide as it is long) and a frontal bone with a wider connection to the upper margin of the orbit. The only living descendants of basal eupelycosaurs are the mammals.

The group was originally considered a suborder of pelycosaurs or "mammal like reptiles", but it was redefined in 1997, and the term pelycosaur itself has fallen into disfavor. We now know that the eupelycosaurs were not in fact reptiles nor of reptile