Phylum Mollusca Linnaeus, 1758 - molluscs
   Conchifera Gegenbaur, 1878 see Subphylum Conchifera Gegenbauer, 1878
     Cyrtosoma
       Class Gastropoda Cuvier, 1795 - snails and slugs
         Subclass †Archaeobranchia Parkhaev, 2001
           Order †Pelagielliformes Runnegar & Pojeta, 1985
             1 Family †Pelagiellidae Knight, 1952
             2 Family †Aldanellidae Linsley & Kier, 1984