ictodosaur vs synapsid

ictodosaur and synapsid both are nouns.

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

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

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

Other hypernyms of ictodosaur include synapsid reptile.

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