Class Mammalia Linnaeus, 1758 - mammals
   Order Rodentia Bowdich, 1821 - rodents
     Suborder Sciurognathi (Tullberg, 1899) see Suborder Sciuromorpha Brandt, 1855
       Family Muridae Batsch, 1788 - rats, mice, hamsters, voles, lemmings, and gerbils
         Subfamily Murinae Batsch, 1788 - Old World mice and rats
           Genus Hydromys Geoffroy Saint-Hilaire, 1804 - beaver-rats
             1 Hydromys chrysogaster E. Geoffroy, 1804 - beaver-rat
             2 Hydromys habbema Tate & Archbold, 1941 - mountain water rat
             3 Hydromys hussoni Musser & Piik, 1982
             4 Hydromys neobrittanicus Tate & Archbold, 1935
             5 Hydromys shawmayeri (Hinton, 1943)