subphylum Vertebrata vs phylum

subphylum Vertebrata and phylum both are nouns.

Word	Noun	Adjective	Verb	Adverb
subphylum Vertebrata	Yes	No	No	No
phylum	Yes	No	No	No

As nouns, phylum is a hypernym of subphylum Vertebrata; that is, phylum is a word with a broader meaning than subphylum Vertebrata:

subphylum Vertebrata: fishes, amphibians, reptiles, birds, mammals
phylum: (biology) the major taxonomic group of animals and plants; contains classes

subphylum Vertebrata (noun)	phylum (noun)
fishes, amphibians, reptiles, birds, mammals	(biology) the major taxonomic group of animals and plants; contains classes
	(linguistics) a large group of languages that are historically related