reptilian vs class Reptilia

reptilian and class Reptilia both are nouns.

Word	Noun	Adjective	Verb	Adverb
reptilian	Yes	Yes	No	No
class Reptilia	Yes	No	No	No

reptilian (noun)	class Reptilia (noun)
any cold-blooded vertebrate of the class Reptilia including tortoises, turtles, snakes, lizards, alligators, crocodiles, and extinct forms	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

reptilian (adjective)	class Reptilia (adjective)
of or relating to the class Reptilia