dolphin vs percoidean

dolphin and percoidean both are nouns.

Word	Noun	Adjective	Verb	Adverb
dolphin	Yes	No	No	No
percoidean	Yes	No	No	No

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

dolphin: large slender food and game fish widely distributed in warm seas (especially around Hawaii)
percoidean: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of dolphin include percoid, percoid fish.

dolphin (noun)	percoidean (noun)
any of various small toothed whales with a beaklike snout; larger than porpoises	any of numerous spiny-finned fishes of the order Perciformes
large slender food and game fish widely distributed in warm seas (especially around Hawaii)