Kingdom Animalia Linnaeus, 1758 - animals
   Phylum Mollusca Linnaeus, 1758 - molluscs
     Subphylum Cyrtosoma Runnegar & Pojeta Jr., 1974 see Phylum Mollusca Linnaeus, 1758
       Class Cephalopoda Cuvier, 1795 - cephalopods
         Subclass Nautiloidea Agassiz, 1848
           Genus †Augustoceras Flower, 1946
           Genus †Bathmoceras Barrande, 1868
           Genus †Byronoceras Foerste & Savage, 1927
           Genus †Cooperoceras Miller, 1945
           Genus †Curtoceras Ulrich, Foerste, Miller & Flower, 1942
           Genus †Cyrtogomphoceras Foerste, 1924
           Genus †Dawsonoceras Hyatt, 1884
           Genus †Discosorus Hall, 1851[1852]
           Genus †Geisonoceras Haytt, 1884
           Genus †Gorbyoceras Shimizu & Obata, 1935
           Genus †Halloceras Hyatt, 1884
           Genus †Lechritrochoceras Foerste, 1926
           Genus †Metacoceras Hyatt, 1884
           Genus †Murrayoceras Foerste, 1926
           Genus †Parakionoceras Foerste, 1928
           Genus †Richardsonoceras Foerste, 1932
           Genus †Westonoceras Foerste, 1926
           1 Order †Ellesemerocerida see Order Ellesmerocerida Flower & Kummel, 1950
           2 Order †Orthocerida Kuhn, 1940