Class [Mammalia] Linnaeus, 1758 - mammals
   Order Rodentia Bowdich, 1821 - rodents
     Family Sciuridae Batsch, 1788 - squirrels, chipmunks, marmots, and prairie dogs
       Subfamily Sciurinae Batsch, 1788 - tree and ground squirrels
         Genus Exilisciurus Moore, 1958 - pygmy squirrels
           1 Exilisciurus concinnus Thomas, 1888 - Philippine pygmy squirrel
           2 Exilisciurus exilis Müller, 1838 - plain pygmy squirrel
           3 Exilisciurus whiteheadi Thomas, 1887 - Whitehead's pygmy squirrel