 The discoveries of synapsid-like openings (see below) in the skull roof of the skulls of several members of Parareptilia (the clade containing most of the amniotes traditionally referred to as "anapsids"), including lanthanosuchoids, millerettids, bolosaurids, some nycteroleterids, some procolophonoids and at least some mesosaurs made it more ambiguous and it's currently uncertain whether the ancestral amniote had an anapsid-like or synapsid-like skull.These animals are traditionally referred to as "anapsids", and form a paraphyletic basic stock from which other groups evolved.Very shortly after the first amniotes appeared, a lineage called Synapsida split off; this group was characterized by a temporal opening in the skull behind each eye to give room for the jaw muscle to move.