extinct vs nonextant

extinct and nonextant both are adjectives.

Word	Noun	Adjective	Verb	Adverb
extinct	No	Yes	No	No
nonextant	No	Yes	No	No

As adjectives, extinct and nonextant are synonyms defined as:

extinct and nonextant: no longer in existence; lost or especially having died out leaving no living representatives

extinct (adjective)	nonextant (adjective)
no longer in existence; lost or especially having died out leaving no living representatives	no longer in existence; lost or especially having died out leaving no living representatives
(of e.g. volcanoes) permanently inactive	no longer existing or inaccessible through loss or destruction
being out or having grown cold