spiny-finned fish vs acanthopterygian

spiny-finned fish and acanthopterygian both are nouns.

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

As nouns, spiny-finned fish and acanthopterygian are synonyms defined as:

spiny-finned fish and acanthopterygian: a teleost fish with fins that are supported by sharp inflexible rays

spiny-finned fish (noun)	acanthopterygian (noun)
a teleost fish with fins that are supported by sharp inflexible rays	a teleost fish with fins that are supported by sharp inflexible rays