polly fish vs percoidean

polly fish and percoidean both are nouns.

Word	Noun	Adjective	Verb	Adverb
polly fish	Yes	No	No	No
percoidean	Yes	No	No	No

As nouns, percoidean is a hypernym of polly fish; that is, percoidean is a word with a broader meaning than polly fish:

polly fish: gaudy tropical fishes with parrotlike beaks formed by fusion of teeth
percoidean: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of polly fish include percoid, percoid fish.

polly fish (noun)	percoidean (noun)
gaudy tropical fishes with parrotlike beaks formed by fusion of teeth	any of numerous spiny-finned fishes of the order Perciformes