noun syn·ap·sid \sə-ˈnap-səd\

Definition of synapsid

  1. :  any of a subclass (Synapsida) of extinct chiefly Permian and Triassic reptiles (as the pelycosaurs) that resembled mammals, had a single pair of lateral temporal skull openings, and are usually held to be ancestral to mammals



Origin and Etymology of synapsid

New Latin Synapsida, from Greek syn- + apsid-, apsis arch, vault — more at apsis

First Known Use: 1956

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