anthoathecata, or the athecate hydroids, are an order of hydrozoans belonging to the phylum cnidaria. a profusion of alternate scientific names exists for this long-known, heavily discussed, and spectacular group. it has also been called gymnoblastea and (with or without an emended ending "-ae"), anthomedusa, athecata, hydromedusa, and stylasterina. there are about 1,200 species worldwide.