Taxonomic status and phylogenetic relationships of Marmosa agilis peruana Tate, 1931 ( Didelphimorphia: Didelphidae), with comments on the morphological variation of Gracilinanus from central-western Brazil.

The marsupials of the family Didelphidae went through profound taxonomic rearrangements in recent decades, mainly related to an increase in the number of specimens deposited in scientific collections and the inclusion of molecular data in systematic analyses, resulting in better resolved phylogenies and taxa delimitation. Analyses of a large series of the gracile mouse opossum Gracilinanus agilis, including types and complementary material, recovered specimens assignable to Marmosa agilis peruana Tate, 1931 as a monophyletic group that is diagnosable by unique morphological, morphometric and molecular datasets, meriting its recognition as a full species. Here we provide an emended diagnosis, description and comparisons with congeners for G. peruanus. The former species differs from the latter by the dull reddish dorsal pelage, smaller general size, position of the maxillary fenestrae, presence of accessory cusps in upper canines, and morphology of the alisphenoid tympanic process. It ranges from central Peru to central Bolivia and western Brazil in the states of Rondônia and northwestern Mato Grosso, where it occurs in sympatry with G. agilis. Many collecting localities lie in areas with high diversity of non-volant small mammals and accelerated deforestation processes, highlighting its importance in terms of biogeographic studies and conservation policies. © 2014 The Linnean Society of London [ABSTRACT FROM AUTHOR]