genus Ceratodus vs fish genus

genus Ceratodus and fish genus both are nouns.

Word	Noun	Adjective	Verb	Adverb
genus Ceratodus	Yes	No	No	No
fish genus	Yes	No	No	No

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

genus Ceratodus: type genus of the Ceratodontidae: extinct genus of lungfishes
fish genus: any of various genus of fish

genus Ceratodus (noun)	fish genus (noun)
type genus of the Ceratodontidae: extinct genus of lungfishes	any of various genus of fish