Abstract:

The Tremarctinae are a subfamily of bears endemic to the New World,including two of the largest terrestrial mammalian carnivores that haveever lived: the giant, short-faced bears Arctodus simus from North Americaand Arctotherium angustidens from South America (greater than or equal to1000 kg). Arctotherium angustidens became extinct during the EarlyPleistocene, whereas Arctodus simus went extinct at the very end of thePleistocene. The only living tremarctine is the spectacled bear (Tremarctosornatus), a largely herbivorous bear that is today only found in SouthAmerica. The relationships among the spectacled bears (Tremarctos), SouthAmerican short-faced bears (Arctotherium) and North American shortfacedbears (Arctodus) remain uncertain. In this study, we sequenced amitochondrial genome from an Arctotherium femur preserved in a Chileancave. Our molecular phylogenetic analyses revealed that the SouthAmerican short-faced bears were more closely related to the extant SouthAmerican spectacled bear than to the North American short-faced bears.This result suggests striking convergent evolution of giant forms in thetwo groups of short-faced bears (Arctodus and Arctotherium), potentially asan adaptation to dominate competition for megafaunal carcasses.

Author affiliation: Mitchell, Kieren J.. University of Adelaide; Australia

Author affiliation: Bray, Sarah C.. University of Adelaide; Australia. University of South Australia; Australia

Author affiliation: Bover, Pere. University of Adelaide; Australia. Consejo Superior de Investigaciones Científicas; España. Universidad de las Islas Baleares. Institut Mediterrani d'Estudis Avançats; España

Author affiliation: Soibelzon, Leopoldo Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina

Author affiliation: Schubert, Blaine W.. East Tennessee State University; Estados Unidos

Author affiliation: Prevosti, Francisco Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; Argentina

Author affiliation: Prieto, Alfredo. Universidad de Magallanes. Instituto de la Patagonia. Centro de Estudios del Hombre Austral; Chile

Author affiliation: Martin, Fabiana Maria. Universidad de Magallanes. Instituto de la Patagonia. Centro de Estudios del Hombre Austral; Chile

Author affiliation: Austin, Jeremy J.. University of Adelaide; Australia

Author affiliation: Cooper, Alan. University of Adelaide; Australia