protomammal vs synapsid

protomammal and synapsid both are nouns.

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

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

protomammal: probably warm-blooded; considered direct ancestor of mammals
synapsid: extinct reptile having a single pair of lateral temporal openings in the skull

Other hypernyms of protomammal include synapsid reptile.

protomammal (noun)	synapsid (noun)
probably warm-blooded; considered direct ancestor of mammals	extinct reptile having a single pair of lateral temporal openings in the skull