A new hyladelphine marsupial (Didelphimorphia, Didelphidae) from cave deposits of northern Brazil

Based on very small upper and lower molars recovered from the Quaternary limestone caves in the State of Tocantins, northern Brazil, we describe a new genus and species of a didelphimorphian marsupial. A phylogenetic analysis based on morphological + karyotypic data set recovered the new genus and species as the sister taxon to the living didelphid, Hyladelphys kalinowskii Voss, Lunde & Simons. The new taxon differs from the latter in having a slightly larger size, more inflated and blunt cusps, greater reduction in number and size of the stylar cusps, in the absence of an anterior cingulum, a deeper ectoflexus in M2, paracone and metacone subequal in M2, and narrower and eccentric protocones. The new marsupial probably weighed no more than 40 g and its molar morphology is suggestive of mixed, insectivorous-frugivorous feeding habits. Although we regard the fauna of Gruta dos Mouras cave as Pleistocene, we do not negate the possibility that a temporal mixing ("time-averaging") of Pleistocene and Holocene specimens existed and that the newly described taxon is a living marsupial in the study area.