Preliminary records on new marsupials from the late Middle Miocene TAR-31 locality, San Martín Department, Peruvian Amazonia

STUTZ, N. S.; ABELLO, M. A.; MARIVAUX, L.; BOIVIN, M.; PUJOS, F.; BENITES PALOMINO, A. M.; SALAS-GISMONDI, R.; TEJADA-LARA, J. V.; RIBEIRO, A. M.

Rio Grande do sul

Congreso; PALEO-RS 2021; 2021

Marsupials, the common name of the members of the infraclass Metatheria, are mammalscurrently distributed in South America, mainly in tropical and subtropical areas, but poorlyrepresented in the fossil record of these regions. Except for the species-rich record of La Venta,Colombia, Miocene metatherians from tropical-equatorial South America are sparsely recortedin Bolivia, Brazil, Peru, and Venezuela. The present study aims at reporting preliminary data onmarsupials recovered from the TAR-31 locality, San Martín Department, Peru. Mammalianbiostratigraphy provided a late middle Miocene (Laventan) age for these findings. At TAR-31,the fossil-yielding layer is a 10 to 15 cm-thick microconglomerate lens, assigned to the lowermember of the Ipururo Formation, which documents the diverse biota of the time, such as seeds,silicified wood, amber clasts, decapod crustaceans, fishes, anurans, turtles, crocodylomorphs,bird, and several mammals. The material was collected using the screen-washing technique (21 mm meshes) and is permanently housed at the Vertebrate Paleontology Department of theMuseo de Historia Natural, Universidad Nacional Mayor San Marcos. Our concerned specimenswere photographed with scanning electron microscope at the Institut des Neurosciences deMontpellier, France. Preliminary identifications allowed the recognition of one tooth of Thylamyscf. colombianus among didelphid didelphimorphs; and three teeth of the palaeothentidPalaeothentes sp. and a new abderitid taxon among paucituberculatans. The presence ofabderitids, as well as that of cebid primates at TAR-31, suggests predominantly wet and warmtropical conditions, with the occurrence of forests in the surroundings. Palaeothentids seeminglypreferred drier habitats, with mixed vegetational cover, which would point, to some extent, to alandscape heterogeneity in the concerned area at that time. Comparisons with other Miocenemetatherian assemblages at low and mid-latitudes of South America clearly point to a closerelationship between TAR-31 and La Venta, as already noticed for other mammalian groups, aswell as with Acre River local fauna and Madre de Dios (MD-67) in Brazil and Peru. The currentresults further the hypothesis of Western Amazonia as a single and consistent biogeographicalregion for land mammals over middle Miocene times, at the edge of the Pebas Mega-WetlandSystem.