gempylid vs percoid

gempylid and percoid both are nouns.

Word	Noun	Adjective	Verb	Adverb
gempylid	Yes	No	No	No
percoid	Yes	No	No	No

As nouns, percoid is a hypernym of gempylid; that is, percoid is a word with a broader meaning than gempylid:

gempylid: snake mackerels; elongated marine fishes with oily flesh; resembles mackerels; found worldwide
percoid: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of gempylid include percoid fish, percoidean.

gempylid (noun)	percoid (noun)
snake mackerels; elongated marine fishes with oily flesh; resembles mackerels; found worldwide	any of numerous spiny-finned fishes of the order Perciformes