A new specimen of Prohegetotherium (Notoungulata, Hegetotheriidae) from the Paleogene of the Subandean (Central Andes), Bolivia

REGUERO, M.; TINEO, D.E.; POIRÉ, D.G.; BONA, P.; PÉREZ, L.M.

Villa de Leyva

Congreso; VI Congreso Latinoamericano de Paleontología de Vertebrados; 2018

Few fossil mammals were known from the Subandean zone or adjoining parts of Bolivia until recently. We report a partial mandible of Prohegetotherium (YPFB LIT-PAL-002) from the outcrops of the Petaca Fm, in the Río Grande River (19°1?17? S - 63°33?25? W) near the town of Abapó, in the southwest of the department of Santa Cruz (Bolivia). This specimen is closely related to Deseadan (late Oligocene) hegetotheriid Prohegetotherium schiaffinoi from Salla (Bolivia), Fray Bentos (Uruguay), Corrientes and Quebrada Fiera (Argentina). Some dental and mandibular characters present in YPFB-LIT-PAL-002 (i.e., the morphology of the shape of the dentary with a marked change in depth along its length increasing in height posteriorly and the size of the m3), illustrate differences with P. schiaffinoi. However, more material is needed to achieve a more precise taxonomic determination of this material, and here we maintain it as Prohegetotherium cf. P. schiaffinoi. Prohegetotherium is especially abundant in the Deseadan deposits of Salla, Bolivia. The new material helps resolve age implications of the fossil mammals previously reported from the Petaca Formation (?Rhynchippus sp.). The hegetotheriid from Petaca probably was a mixed feeder, consuming a variable diet obtained close to the ground subjected to an abrasive covering of dust and grit. The depositional setting of the Petaca Formation corresponds to mobile channels belts, where the width/thickness relationship of the channel bodies in cross-section, are characterized by broad ribbons forms. In many channels bodies, it is possible to recognize rhizoconcretions and carbonates nodules, which indicate that these fluvial systems developed under semi-arid climates. This unit represents the initial filling stages of the Chaco foreland basin, during the late Oligoceneearly Miocene.