Atlantidosteus is an extinct genus of homostiid arthrodire from the Early to Middle Devonian of Morocco and Queensland.[1] It contains two known species, A. hollardi and A. pacifica.
Atlantidosteus pacifica is known from a right suborbital plate, found in the Broken River Group of Queensland, Australia.
Atlantidosteus is part of the clade Migmatocephala, closer related to Homostius, than Antineosteus.