genus Ursus vs mammal genus

genus Ursus and mammal genus both are nouns.

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

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

genus Ursus: type genus of Ursidae: brown bears; in some classifications genus Ursus includes all bears
mammal genus: a genus of mammals

genus Ursus (noun)	mammal genus (noun)
type genus of Ursidae: brown bears; in some classifications genus Ursus includes all bears	a genus of mammals