New reports, updates, and additional comments about Neobrachytherium ullumense Soria, 2001 (Litopterna, Proterotheriidae) in the Late Miocene of Uruguay and Argentina

Abstract

We describe new proterotheriid specimens from three Late Miocene lithostratigraphic units: the Camacho Formation of Uruguay and the Loma de Las Tapias and Cerro Azul formations of Argentina. The remains include skull and mandibular fragments as well as postcranial remains. The type of Neobrachytherium ullumense is described for the first time, and we expand its diagnosis, judging the following combination of characteristics to be diagnostic: slender and short skull; in lateral view the plane of the dorsal surface and occlusal plane of the rostrum converge on the anterior end; premaxilla anteriorly projected, not diverging from the sagittal plane; slender zygomatic arch; orbit with rostral border at the level of the posterior root of M1; occipital condyles are ventrally projected; P3-P4 with anterolingual cingulum extended are distally; M2 with a reduced metaconule of the circular base, interrupting the posterolingual groove; M3 with a well-developed hypocone separated from the protocone by a posterolingual groove and without metaconule; p4-m3 with a short trigonid and free entoconid, variably positioned relative to the hypolophulid, with paraconid oriented towards the metaconid, and cristid obliqua closing at the metaconid level. A better understanding of the diversity of the family Proterotheriidae, and especially their dental morphology, including the shape, position and development of cusps and valleys, is provided. Neobrachytherium ullumense had been previously reported for Late Miocene, in the South American Land Mammal Ages Chasicoan and Huayquerian, in levels of the San Juan (Loma de Las Tapias Formation) and Buenos Aires (Cerro Azul Formation) provinces of Argentina. This contribution expands the geographic distribution of the species 500 km East, to San José Department (Camacho Formation), Uruguay.