Definition of "synapsid" [synapsid]

• Pertaining to the class Synapsida, of animals which have an opening low in the skull roof behind each eye, leaving a bony arch beneath each. (adjective)
• Any animal (including all mammals) of the class Synapsida. (noun)

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• "The term "synapsid" is increasingly used cladistically, including mammals -- thus, synapsids are not extinct at all."
• "I was under the impression that “therapsid” always referred to a kind of synapsid reptile and was distinct from “pelycosaur” another kind of synapsid think dimetrodon."
• "Otherwise, we have more of the lumbering and vaguely stegosaur-like "stegodons" seen elsewhere in Azeroth and a bizarre mutation of basilisk that they're calling "Diemetradon" (clearly loosely inspired by the Permian-aged Dimetrodon, which, you'll note, isn't a dinosaur, but, rather, a pelycosaurian synapsid)."