anapsid vs chelonian

anapsid and chelonian both are nouns.

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

As nouns, chelonian is a hyponym of anapsid; that is, chelonian is a word with a more specific, narrower meaning than anapsid:

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

Other hyponyms of anapsid include chelonian reptile.

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

anapsid (adjective)	chelonian (adjective)
	of or relating to or resembling or being a turtle or tortoise