Vertebrata Cuvier, 1812 - vertebrates
   Gnathostomata
     Teleostomi
       Tetrapoda Hatschek & Cori 1896 [Gauthier, Kluge & Rowe 1988]
         Amniota Haeckel, 1866 [Gauthier, Kluge & Rowe 1988] - amniotes
           Class Mammalia Linnaeus, 1758 - mammals
             Subclass Theria Parker & Haswell, 1897
               Theria of Metatherian-Eutherian grade
                 Infraclass Eutheria Gill, 1872
                   Order Cetacea Brisson, 1762 - whales, dolphins, and porpoises see Infraorder Cetacea Brisson, 1762
                     Suborder Mysticeti Cope, 1891 - baleen whales see Parvorder Mysticeti Cope, 1891
                       1 Family †Aetiocetidae Emlong, 1966
                       2 Family †Cetotheriidae Brandt, 1872
                       3 Family Eschrichtiidae Ellerman & Morrison-Scott, 1951 - gray whales
                       4 Family Balaenopteridae Gray, 1864 - rorquals
                       5 Family Balaenidae Gray, 1821 - right whales