genus Gerbillus vs mammal genus

genus Gerbillus and mammal genus both are nouns.

Word	Noun	Adjective	Verb	Adverb
genus Gerbillus	Yes	No	No	No
mammal genus	Yes	No	No	No

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

genus Gerbillus (noun)	mammal genus (noun)
type genus of the Gerbillinae: typical gerbils	a genus of mammals