dinosaur vs archosaur

dinosaur and archosaur both are nouns.

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

As nouns, archosaur is a hypernym of dinosaur; that is, archosaur is a word with a broader meaning than dinosaur:

dinosaur: any of numerous extinct terrestrial reptiles of the Mesozoic era
archosaur: extinct reptiles including: dinosaurs, plesiosaurs, pterosaurs, ichthyosaurs, thecodonts

Other hypernyms of dinosaur include archosaurian, archosaurian reptile.

dinosaur (noun)	archosaur (noun)
any of numerous extinct terrestrial reptiles of the Mesozoic era	extinct reptiles including: dinosaurs, plesiosaurs, pterosaurs, ichthyosaurs, thecodonts