gallinacean vs hoatzin

gallinacean and hoatzin both are nouns.

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

As nouns, hoatzin is a hyponym of gallinacean; that is, hoatzin is a word with a more specific, narrower meaning than gallinacean:

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

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