chelonian reptile vs anapsid

chelonian reptile and anapsid both are nouns.

Word	Noun	Adjective	Verb	Adverb
chelonian reptile	Yes	No	No	No
anapsid	Yes	No	No	No

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

chelonian reptile: a reptile of the order Chelonia
anapsid: primitive reptile having no opening in the temporal region of the skull; all extinct except turtles

Other hypernyms of chelonian reptile include anapsid reptile.

chelonian reptile (noun)	anapsid (noun)
a reptile of the order Chelonia	primitive reptile having no opening in the temporal region of the skull; all extinct except turtles