subphylum Vertebrata vs bird genus

subphylum Vertebrata and bird genus both are nouns.

Word	Noun	Adjective	Verb	Adverb
subphylum Vertebrata	Yes	No	No	No
bird genus	Yes	No	No	No

subphylum Vertebrata (noun)	bird genus (noun)
fishes, amphibians, reptiles, birds, mammals	a genus of birds