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
               Family †Stenothecidae Runnegar & Jell, 1980
                 .1 Genus †Anabarella Vostokova, 1962
                 .2 Genus †Eurekapegma MacKinnon, 1985
                 .3 Genus †Mellopegma Runnegar & Jell, 1976
                 .4 Genus †Stenotheca Salter, 1872
                 .5 Genus †Watsonella Grabau, 1900
                 1 Subfamily †Stenothecinae Runnegar & Jell, 1980
                 2 Subfamily †Watsonellinae Parkhaev, 2001