Reptilia vs reptilian

Reptilia and reptilian both are nouns.

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

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

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