archosaurian reptile vs archosaur

archosaurian reptile and archosaur both are nouns.

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

As nouns, archosaurian reptile and archosaur are synonyms defined as:

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

Other synonyms of archosaurian reptile include archosaurian.

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