hexapod vs fauna

hexapod and fauna both are nouns.

Word	Noun	Adjective	Verb	Adverb
hexapod	Yes	No	No	No
fauna	Yes	No	No	No

As nouns, fauna is a hypernym of hexapod; that is, fauna is a word with a broader meaning than hexapod:

Other hypernyms of hexapod include animal, animate being, beast, brute, creature.

hexapod (noun)	fauna (noun)
an animal having six feet	a living organism characterized by voluntary movement
	all the animal life in a particular region or period