class Reptilia vs subclass Archosauria

class Reptilia and subclass Archosauria both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Reptilia	Yes	No	No	No
subclass Archosauria	Yes	No	No	No

class Reptilia (noun)	subclass Archosauria (noun)
class of cold-blooded air-breathing vertebrates with completely ossified skeleton and a body usually covered with scales or horny plates; once the dominant land animals	a large subclass of diapsid reptiles including: crocodiles, alligators, dinosaurs, pterosaurs, plesiosaurs, ichthyosaurs, thecodonts