synapsid reptile vs reptile

synapsid reptile and reptile both are nouns.

Word	Noun	Adjective	Verb	Adverb
synapsid reptile	Yes	No	No	No
reptile	Yes	No	No	No

As nouns, reptile is a hypernym of synapsid reptile; that is, reptile is a word with a broader meaning than synapsid reptile:

synapsid reptile: extinct reptile having a single pair of lateral temporal openings in the skull
reptile: any cold-blooded vertebrate of the class Reptilia including tortoises, turtles, snakes, lizards, alligators, crocodiles, and extinct forms

Other hypernyms of synapsid reptile include reptilian.

synapsid reptile (noun)	reptile (noun)
extinct reptile having a single pair of lateral temporal openings in the skull	any cold-blooded vertebrate of the class Reptilia including tortoises, turtles, snakes, lizards, alligators, crocodiles, and extinct forms