batfish vs spiny-finned fish

batfish and spiny-finned fish both are nouns.

Word	Noun	Adjective	Verb	Adverb
batfish	Yes	No	No	No
spiny-finned fish	Yes	No	No	No

As nouns, spiny-finned fish is a hypernym of batfish; that is, spiny-finned fish is a word with a broader meaning than batfish:

batfish: bottom-dweller of warm western Atlantic coastal waters having a flattened scaleless body that crawls about on fleshy pectoral and pelvic fins
spiny-finned fish: a teleost fish with fins that are supported by sharp inflexible rays

Other hypernyms of batfish include acanthopterygian.

batfish (noun)	spiny-finned fish (noun)
bottom-dweller of warm western Atlantic coastal waters having a flattened scaleless body that crawls about on fleshy pectoral and pelvic fins	a teleost fish with fins that are supported by sharp inflexible rays