Résumé
Currently , marsupials show great species richness and abundance in the Amazonian region. However, little is known about their evolutionary history in this region, as their sparse fossil record is restricted to a few Cenozoic Amazonian localities. Decades of fieldwork in Peruvian Amazonia allowed for the discovery of several Eocene–Oligocene localities in the Contamana and Huallaga Basin regions, where profuse assemblages of fossil metatherians were discovered. Here, we introduce a new family of polydolopimorphian metatherians, Wamradolopidae, to which we ascribe a new species, Wamradolops telloi, and a new genus and species, Pozodolops manuelorum. Cladistic analyses provided support for the recognition of these new taxa and revealed close affinities among them and with Wamradolops tsullodon Goin & Candela, 2004 , a taxon previously described from the early Oligocene of Santa Rosa, also in Peruvian Amazonia. Wamradolopids are an early-diverging polydolopimorphian clade, falling outside the traditionally recognized suborders of the latter, i.e., Bonapartheriiformes and Polydolopiformes, which we did not recover as monophyletic clades. Polydolopimorphians seem to have close phylogenetic relationships with Australidelphia, a clade which includes the South American Microbiotheria and all extant marsupials from Australasia. Wamradolopids were seemingly restricted to tropical-equatorial lowlands of South America and had diminutive size – we estimated their body mass to range 3–55 g. They further were a conspicuous component of marsupial, metatherian and mammalian assemblages at low latitudes of South America over Paleogene times, likely with considerable distribution and abundance. This new record highlights the distribution and diversity of Amazonian polydolopimorphians, which had so far remained unknown. It further provides support for the hypothesis of “Proto-Amazonian” and “Patagonian” mammals having experienced distinct diversity patterns and evolutionary trajectories over Cenozoic times, much of it yet to discover.