archosaur vs archosaurian

archosaur and archosaurian both are nouns.

Word	Noun	Adjective	Verb	Adverb
archosaur	Yes	No	No	No
archosaurian	Yes	Yes	No	No

As nouns, archosaur and archosaurian are synonyms defined as:

archosaur and archosaurian: extinct reptiles including: dinosaurs, plesiosaurs, pterosaurs, ichthyosaurs, thecodonts

Other synonyms of archosaur include archosaurian reptile.

archosaur (noun)	archosaurian (noun)
extinct reptiles including: dinosaurs, plesiosaurs, pterosaurs, ichthyosaurs, thecodonts	extinct reptiles including: dinosaurs, plesiosaurs, pterosaurs, ichthyosaurs, thecodonts

archosaur (adjective)	archosaurian (adjective)
	of or relating to reptiles of the subclass Archosauria