Résumé
Metatheria (Mammalia) include living marsupials plus stem clades closer to them than to placental mammals. They have a Cenozoic evolutionary history in South America characterized by several phases of diversification and extinction. Today, their diversity is dramatically reduced compared to the past one. However, due to substantial gaps in the fossil record, especially for low-latitudes of this landmass, much is still unknown. Several new Paleogene localities in Peruvian Amazonia have yielded fossil metatherians, primarily documenting the order Polydolopimorphia. Among these, is Wamradolops tsullodon, of uncertain phylogenetic affinities, formerly described and only known at Santa Rosa (early Oligocene, Peruvian Amazonia). Our new fossil material provided the same species, as well as a new related species, yet to be described. Both are abundant and widespread at the studied outcrops, enabling the observation of intraspecific morphological variation (e.g., size, presence/absence of cinguli, or stylar cusps). Preliminary phylogenetic analyses, including an unprecedented amount of polydolopimorphians, suggest that the order may be polyphyletic. Wamradolops is monophyletic and phylogenetically close to Prepidolopidae. This family, plus Argyrolagidae and Polydolopidae, are retrieved as belonging to the Australidelphia clade. Further analyses should help elucidating the Polydolopimorphia puzzle and the role the proto-Amazonian region played in the evolution of metatherians.