A class of Crustacea whose application is gaining moderately widespread use, despite the fact that its validity is not universally accepted by researchers. The constituent subclasses of the Maxillopoda also remain unsettled: before 1956, all major subclasses of the Crustacea were regarded as distinct taxa of equal rank. In addition to the Malacostraca, these included the Cephalocarida, Branchiopoda, Cirripedia, Copepoda, Mystacocarida, Branchiura, and Ostracoda. Use of cladistics, or phylogenetic analysis, has rekindled interest in phylogenetic relationships and hierarchy among the nonmalacostracan taxa.