bony fish vs lobefin

bony fish and lobefin both are nouns.

Word	Noun	Adjective	Verb	Adverb
bony fish	Yes	No	No	No
lobefin	Yes	No	No	No

As nouns, lobefin is a hyponym of bony fish; that is, lobefin is a word with a more specific, narrower meaning than bony fish:

bony fish: any fish of the class Osteichthyes
lobefin: any fish of the order Crossopterygii; most known only in fossil form

Other hyponyms of bony fish include crossopterygian, lobe-finned fish, lungfish, teleost, teleost fish, teleostan.

bony fish (noun)	lobefin (noun)
any fish of the class Osteichthyes	any fish of the order Crossopterygii; most known only in fossil form