autochthonic vs endemic

autochthonic is not a noun while endemic is a noun.

Word	Noun	Adjective	Verb	Adverb
autochthonic	No	Yes	No	No
endemic	Yes	Yes	No	No

As adjectives, autochthonic and endemic are synonyms defined as:

Other synonyms of autochthonic include autochthonal, autochthonous, indigenous.

autochthonic (noun)	endemic (noun)
	a plant or animal that is native to a certain limited area
	a disease that is constantly present to a greater or lesser degree in people of a certain class or in people living in a particular location

autochthonic (adjective)	endemic (adjective)
originating where it is found	of or relating to a disease (or anything resembling a disease) constantly present to greater or lesser extent in a particular locality
	native to or confined to a certain region
	originating where it is found