A large opossum (Didelphimorphia, Didelphidae) for the Late Pleistocene of Uruguay (Sopas Formation).

MANZUETTI, A.; RINDERKNECHT, A.; PEREA, A.; GHIZZONI, M.; UBILLA, M.; VEZZOSI, R.I.

París

Congreso; 5th International Palaeontological Congress; 2018

International Paleontological Association

The fossil record ofmarsupials in the Quaternary of Uruguay not only is scarce but also the previousrecords have weak stratigraphic information and the material is lost. Here aredescribed the first remains with precise stratigraphic information for theUruguayan Quaternary (Sopas Formation, Late Pleistocene), assigned to a largeopossum of the genus Didelphis. Thematerials are housed in the Paleontological Collection of the Facultad deCiencias, Montevideo (FC-DPV) and in the Ghizzoni Collection of Salto (G). The specimensfound consist of a partial portion of the skull associated to mandible and somepostcranial bones (FC-DPV 875) (Sopas Creek, Salto department), and both humeri,a complete ulna and part of the other, an incomplete femur, and some vertebrae(G 80-1) (Arapey Chico River, Salto department). Both specimens are adults. OSLand radiocarbon ages of the Sopas Formation are mostly related to the interval60 to 30 kyr BP, correlated with the last interstadial (MIS-3) of the LatePleistocene. The morphology and dimensions of skull, mandible and postcranialbones (FC-DPV 875) support the assignation to a large opossum. The skull has anelongated and gracile rostral region, in the mandible the angular process isinteriorly inflexed and upper and lower dentition, even worm, show the typicalmetatherian basic sectorial morphology. The humeri and ulnae are robust, large,and very well preserved. Preliminary comparisons of humeri (G 80-1) indicatemany similarities with large opossums of Didelphisgenus. Body mass estimations based on upper and lower dentition allometricequations for extant marsupials are congruent with the referred genus. Themultivariate analysis performed over skull and mandible measures show similarresults. Didelphis has greattolerance to diverse habitats conditions, occupying in current times different environmentsas wooded areas, open contexts and arid to temperate climates but closely to freshwaterbodies, which is congruent with environment and climate conditions proposed forthe Sopas Formation. It is a success generalist feeder, occupying an importantrole in intermediate levels of the trophic chain.