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 Sigmodontinae Wagner, 1843
           Genus Isthmomys Hooper & Musser, 1964 - yellow deer mouse and Mount Pirri deer mouse
             1 Isthmomys flavidus Bangs, 1902 - yellow deer mouse
             2 Isthmomys pirrensis Goldman, 1912 - Mount Pirri deer mouse