Branchiostegidae vs fish family

Branchiostegidae and fish family both are nouns.

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

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

Branchiostegidae (noun)	fish family (noun)
small family of marine fishes having covered gills	any of various families of fish