thecodont vs archosaurian

thecodont and archosaurian both are nouns.

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

As nouns, archosaurian is a hypernym of thecodont; that is, archosaurian is a word with a broader meaning than thecodont:

thecodont: presumably in the common ancestral line to dinosaurs and crocodiles and birds
archosaurian: extinct reptiles including: dinosaurs, plesiosaurs, pterosaurs, ichthyosaurs, thecodonts

Other hypernyms of thecodont include archosaur, archosaurian reptile.

thecodont (noun)	archosaurian (noun)
presumably in the common ancestral line to dinosaurs and crocodiles and birds	extinct reptiles including: dinosaurs, plesiosaurs, pterosaurs, ichthyosaurs, thecodonts

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