megapode vs gallinacean

megapode and gallinacean both are nouns.

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

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

megapode: large-footed short-winged birds of Australasia; build mounds of decaying vegetation to incubate eggs
gallinacean: heavy-bodied largely ground-feeding domestic or game birds

Other hypernyms of megapode include gallinaceous bird.

megapode (noun)	gallinacean (noun)
large-footed short-winged birds of Australasia; build mounds of decaying vegetation to incubate eggs	heavy-bodied largely ground-feeding domestic or game birds