A New Toxodont from the Raigón Formation (Plio-Pleistocene) of Uruguay

FERRERO BRENDA SOLEDAD; SCHMIDT GABRIELA INÉS; PEREZ GARCÍA MARÍA MARÍA INÉS; RIBEIRO ANA MARÍA; PEREA DANIEL

Mendoza

Congreso; 4th International Palaentological Congress; 2014

The specimen FC-DPV-514 (Facultad de Ciencias, Paleontología de Vertebrados, Uruguay) from the San José Member of the Raigón Formation (Plio-Pleistocene) consists in a skull fragment with P3-M3, right mandible with i1, m1-m3 and postcranial fragments. This specimen was referred to Dinotoxodon paranensis (originally described from ?Mesopotamiense? late Miocene, Entre Ríos Province, Argentina) based on the ventral extension of the mandibular ramus. MLP 39-XII-2-8 (stored at Museo de La Plata, Buenos Aires, Argentina), from ?Mesopotamiense?, also shares this feature, but it is less marked than in FC-DPV-514, and its maximum height is at m2 level. FC-DPV-514 shows m2 with well-developed metaconid and straight posterior edge. The entolophid of m3 is straight, the hypoconulid is longer than MLP 39-XII-2-8, and lacks a smooth labial groove opposite to ento-hypoconid fold. These differences would dismiss the assignation of FC-DPV-514 to Dinotoxodon. Moreover, FC-DPV-514 differs from other Miocene taxa with ventral extension of the mandible: Gyrinodon and Pericotoxodon have the lower edge less marked than FC-DPV-514, whereas in Hoffstetterius this feature is the most developed. In Gyrinodon and Hoffstetterius the maximum height of the mandible is at the anterior region of m3, whereas in Pericotoxodon it is at the level of m2, and in FCD-DPV-514 it is at the posterior region of m3. Furthermore, in FC-DPV-514 the hypoconulid (m1-m2) is lingually extended as observed in Toxodon and Pisanodon, differing of Gyrinodon, Pericotoxodon, Calchaquitherium, and Ocnerotherium (m2). Although Hoffstetterius has the hypoconulid lingually extended, it is less marked in m1 and rounded in m2. Unlike FCD-DPV-514, Haplodontherium and Trigodon only show the ento-hypoconid fold in m1-m2, Trigodonops presents the meta-entoconid fold hardly developed in m1-m2, and it is barely developed only in m2 of Mixotoxodon. Plesiotoxodon and Hemixotodon differ from FC-DPV-514 in the ectoloph morphology in M2-M3, the M2 has the anterior and posterior grooves well-developed, and they have an Y-shaped convergence. Stenotephanos, Posnanskytherium, Hyperoxotodon, Hemixotodon, and Nonotherium are smaller than FC-DPV-514, with shorter and lingually extended paraconid. These morphological differences would support the erection of a new toxodontid genus in Uruguay. FCD-DPV-514 belongs to a fauna from the Raigón Formation that includes the endemic Giganhinga kiyuensis, Pronothrotherium figueirasi, Josephoartigasia and the Plio-Pleistocene Platygonus. Moreover, the finding of Glyptodon, Plaxhaphous, and Catonyx tarijensis in this formation would indicate a Pleistocene age so it would be considered Pliocene-Pleistocene in age according to its faunistic content. Contribution to PIP-CONICET-112-201101-01024; FCE-2011-6752; CNPq/PQ-312085/2013-3.