subphylum Craniata vs mammal genus

subphylum Craniata and mammal genus both are nouns.

Word	Noun	Adjective	Verb	Adverb
subphylum Craniata	Yes	No	No	No
mammal genus	Yes	No	No	No

subphylum Craniata (noun)	mammal genus (noun)
fishes, amphibians, reptiles, birds, mammals	a genus of mammals