Class Mammalia Linnaeus, 1758 - mammals
   Order Marsupialia Jameson, 1818 - marsupials see Cohort Marsupialia Jameson, 1818
     Family Didelphidae Gray, 1821 - American opossums
       Genus Marmosa Gray, 1821 - murine opossums
         Subgenus Thylamys Gray, 1843 see Genus Thylamys Gray, 1843
           Marmosa elegans group see Genus Thylamys Gray, 1843
             Marmosa formosa Shamel, 1930, nom. illeg. see Gracilinanus agilis (Burmeister, 1854)