family Myxinidae vs fish family

family Myxinidae and fish family both are nouns.

Word	Noun	Adjective	Verb	Adverb
family Myxinidae	Yes	No	No	No
fish family	Yes	No	No	No

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

family Myxinidae (noun)	fish family (noun)
slime-producing marine animals: hagfishes	any of various families of fish