Revisión sistemática de los Tremarctinae (Carnivora, Ursidae) fósiles de América del Sur

The systematics, and the geographic and stratigraphic distribution of the South American fossil taxa of Tremarctinae (Carnivora, Ursidae) are reviewed and discussed. New diagnostic characters are proposed, in order to support each taxon. Only one genus (Arctotherium), of the Pleistocene and Lower Holocene of South America, is recognized, with five species: A. vetustum Ameghino, A. wingei Ameghino, A. angustidens Gervais & Ameghino, A. bonariense (Gervais), and A. tarijense Ameghino. Arctotherium is recorded from the Ensenadan (Upper Pliocene to Middle Pleistocene) to the Lujanian (Upper Pleistocene to Lower Holocene) in Venezuela, Brazil, Bolivia, Uruguay, Argentina, and Chile. A. vetustum is recorded in the Bonaerian (Middle Pleistocene) in Argentina; A. wingei in the Lujanian in Venezuela, Bolivia and Brazil; A. angustidens in the Ensenadan of Bolivia and Argentina; A. bonariense in the Bonaerian and Lujanian of Argentina and A. tarijense in the Bonaerian and Lujanian of Uruguay, Argentina, and Chile. Arctotherium is characterized by ten features: the post palatine margin slightly overpasses the distal end of M2, P1-3 compressed in a triangular arrangement, protocone reduced or absent in P4, length between canine and P4 less than P4 mesio-distal length, metastyle reduced or absent in M1, M2 wider than in other ursids, p4 crown ellipsoidal shaped, m1 trigonid wider than in other ursids, m2 crown kidney shaped, m3 crown sub circulate shaped. Museo de La Plata