hoatzin vs gallinacean

hoatzin and gallinacean both are nouns.

Word	Noun	Adjective	Verb	Adverb
hoatzin	Yes	No	No	No
gallinacean	Yes	No	No	No

As nouns, gallinacean is a hypernym of hoatzin; that is, gallinacean is a word with a broader meaning than hoatzin:

hoatzin: crested ill-smelling South American bird whose young have claws on the first and second digits of the wings
gallinacean: heavy-bodied largely ground-feeding domestic or game birds

Other hypernyms of hoatzin include gallinaceous bird.

hoatzin (noun)	gallinacean (noun)
crested ill-smelling South American bird whose young have claws on the first and second digits of the wings	heavy-bodied largely ground-feeding domestic or game birds