ac·an·tho·di·an I. adjective alsoac·an·tho·de·an\|aˌkan|thōdēən, |akən-\ Etymology: New Latin Acanthodii, Acanthodei + English -an : of or belonging to the subclass Acanthodii II. noun alsoacanthodean\“\ (-s) : an animal or fossil belonging to the subclass Acanthodii