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 †Helcionelliformes Golikov & Starobogatov, 1975
             Superfamily †Yohelcionelloidea nom. null. see Superfamily Yochelcionelloidea Runnegar & Jell, 1976
               1 Family †Yochelcionellidae Runnegar & Jell, 1976
               2 Family †Trenellidae Parkhaev, 2001
               3 Family †Stenothecidae Runnegar & Jell, 1980