Class Mammalia Linnaeus, 1758 - mammals
   Subclass Theria Parker & Haswell, 1897
     Order Sirenia Gill, 1872 - sea cows
       Family Dugongidae Gray, 1821 - dugong and sea cow
         Subfamily ‡Hydrodamalinae Palmer, 1895
           1 Genus ‡Hydrodamalis Retzius, 1794 - Steller's sea cow, great northern sea cow