synapsid vs ictodosaur

synapsid and ictodosaur both are nouns.

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

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

synapsid: extinct reptile having a single pair of lateral temporal openings in the skull
ictodosaur: intermediate in form between the therapsids and most primitive true mammals

Other hyponyms of synapsid include protomammal, therapsid, pelycosaur, edaphosaurus, dimetrodon.

synapsid (noun)	ictodosaur (noun)
extinct reptile having a single pair of lateral temporal openings in the skull	intermediate in form between the therapsids and most primitive true mammals