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Almost all large carnivorans (Carnivora; > 20 kg) that inhabited South America became extinct around the Late Pleistocene–Early Holocene transition. Two exceptions were species of coyote-sized Dusicyon, one insular (D. australis) and one continental (D. avus). The extinction of the former is a resolved matter, but that of D. avus, found in the Patagonian and Pampean regions, is still poorly understood. Using the Gaussian-Resampled Inverse-Weighted McInerny method we present new radiocarbon evidence indicating that its disappearance occurred in very recent times (about 324–496 years cal BP. We found no evidence to support a role for hybridization with domestic dogs in causing the extirpation of this fox. Climatic change may have reduced its distributional range, as has happened with other mammals, although not to the extent of explaining its extinction. Climatic change, however, coupled with increased anthropogenic impacts such as hunting, domestic dogs, and/or other aspects relating to the impact of European colonization in South America's southern cone, were the probable main drivers of the recent extinction of D. avus. Fil: Prevosti, Francisco Juan. Universidad Nacional de Luján; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina. 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 Fil: Ramirez, Mariano Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina Fil: Schiaffini, Mauro Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagóica. Universidad Nacional de la Patagonia ; Argentina Fil: Martin, Fabiana Maria. Universidad de Magallane; Chile Fil: Udrizar Sauthier, Daniel Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina Fil: Carrera, Marcelo. Universidad Nacional de la Patagonia. Facultad de Ciencias Naturales. Sede Puerto Madryn; Argentina Fil: Sillero-Zubiri, Claudio. University of Oxford; Reino Unido Fil: Pardiñas, Ulises Francisco J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina

During the late Pleistocene, Patagonia had a rich fauna of large mammals including some megamammals such as ground sloths (Mylodon darwini), horse (Hippidion saldiasi), and camelids (e.g., Lama guanicoe). The carnivore guild was represented by several extinct taxa such as the sabretooth cat (Smilodon), the Patagonian Panther (Panthera onca mesembrina), a short-faced bear (Arctotherium tarijense) and a large fox (Dusicyon avus), but also by the extant puma (Puma concolor). In order to reconstruct the relationships within the predator guild and between these carnivores and their potential prey, body size, prey size and diet habits of each predator were estimated. These results are complemented with stable isotopic analyses and taphonomic information. Results indicate that the guild was composed of three felids that were large hypercarnivores, two of which (Smilodon, P. onca) could prey on most large mammals. Morphology suggests that the short-faced bear was mainly an omnivore that may have scavenged and occasionally hunted medium-large mammals like camelids and horses. D. avus was slightly larger and more carnivorous than the living culpeo fox (Lycalopex culpaeus), and preyed mostly on small mammals (rodents) but occasionally on camelids. Stable isotopes (δ13C and δ15N) are congruent with these interpretations, although they indicate that Arctotherium and D. avus were highly carnivorous. This could be explained by scavenging habits. Stable isotopes also indicate that P. o. mesembrina ate larger proportions of Hippidion and Lama gracilis. Taphonomic studies showed that P. o. mensembrina gnawed bones of Mylodon, Hippidion and camelids, a result that suggests that these taxa were common prey, and agrees with the ecomorphological and stable isotope interpretations. The diversity of potential prey is lower than that observed in lower latitudes (e.g., Pampean Region) while the number of predators is similar, a relationship that could be explained by the high latitude where these mammals lived. Fil: Prevosti, Francisco Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina Fil: Martin, Fabiana Maria. Instituto de la Patagonia; Chile

The origins of the extinct Falkland Islands wolf (FIW), Dusicyon australis, have remained a mystery since it was first recorded by Europeans in the seventeenth century. It is the only terrestrial mammal on the Falkland Islands (also known as the Malvinas Islands), which lie ∼460 km from Argentina, leading to suggestions of either human-mediated transport or overwater dispersal. Previous studies used ancient DNA from museum specimens to suggest that the FIW diverged from its closest living relative, the South American maned wolf (Chrysocyon brachyurus) around 7 Ma, and colonized the islands ∼330 ka by unknown means. Here we retrieve ancient DNA from subfossils of an extinct mainland relative, Dusicyon avus, and reveal the FIW lineage became isolated only 16 ka (8-31 ka), during the last glacial phase. Submarine terraces, formed on the Argentine coastal shelf by low sea-stands during this period, suggest that the FIW colonized via a narrow, shallow marine strait, potentially while it was frozen over., Facultad de Ciencias Naturales y Museo

The fossil record of foxes in South America is very rich, with almost all extant South American species recorded. Currently, three fossil species are known in the Plio-Pleistocene of South America: "Dusicyon" cultridens, Dusicyon avus and "Canis" ensenadensis. In the present work we reviewed the systematics of "Canis" ensenadensis from the Pleistocene of Buenos Aires province using both qualitative and quantitative approaches. We also described a new fossil specimen (MCA 2082) from Buenos Aires Province (Argentina) that shares some similarities with "Canis" ensenadensis. We compared the fossil specimens with a large sample of specimens that includes the living species Lycalopex gymnocercus, L. culpaeus, Cerdocyon thous, L. fulvipes, L. vetulus, L. sechurae and Atelocynus microtis. We performed a Principal Component Analysis using mandibular and dental measurements, and then a geometric morphometric analysis using photographs of the lateral view of the mandible. Our results indicate that "Canis" ensenadensis is a valid species and it should be included in the genus Lycalopex. We also conclude that MCA 2082 is a member of the genus Lycalopex, probably belonging to the species L. ensenadensis. These results suggest that the biochron of L. ensenadensis reaches the Lujanian Age. Even if our assignation of MCA 2082 is incorrect, this specimen represents a different taxon from those already described for the Lujanian, thus the diversity of foxes during the Lujanian is greater than previously known. El registro fósil de zorros en América del Sur es muy rico con prácticamente todas las especies sur americanas actuales representadas en él. En la actualidad se conocen tres especies extintas para el Plio-Pleistoceno de América del Sur. “Dusicyon” cultridens, Dusicyon avus y “Canis” ensenadensis. En el presente trabajo hemos reestu- diado la sistemática de “Canis” ensenadensis del Pleistoceno de la provincia de Buenos Aires abordando enfoques cualitativos y cuantitativos. Además describimos un nuevo espécimen proveniente de la Provincia de Buenos Aires (Argentina) que comparte ciertas características con “Canis” ensenadensis. Los especímenes fósiles fueron comparados con una gran muestra de especímenes actuales correspondientes a las espe- cies L. gymnocercus, L. culpaeus, Cerdocyon thous, L. fulvipes, L. vetulus, L. sechurae y Atelocynus microtis. Se realizó un Análisis de Componentes Principales, utilizando medidas mandibulares y dentarias, y un análisis de morfometría geométrica, utilizando fotografías de vistas laterales de la mandíbula. Nuestros resultados sugieren que “Canis” ensenadensis es una especie válida y que debe ser incluida en el género Lycalopex. Además concluímos que MCA 2082 es un miembro del género Lycalopex, perteneciendo tentativamente a la especie Lycalopex ensenadensis. Esto sugiere que el biocrón de Lycalopex ensenadensis alcanzaría la Edad Lujanense. Incluso si nuestra asignación fuese incorrecta, el espéci- men representaría una especie distinta a las descriptas para el Lujanense, por lo que la diversidad de zorros del Lujanense es mayor a la pre- viamente conocida. Fil: Ramirez, Mariano Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "bernardino Rivadavia"; Argentina Fil: Prevosti, Francisco Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "bernardino Rivadavia"; Argentina. Universidad Nacional de Luján; Argentina

The fossil record of Canidae in South America begins in the Late Pliocene. During the Pleistocene large hypercarnivorecanids (Theriodictis, Protocyon, Canis dirus) and also large species of Neotropical foxes (Dusicyon avus) evolved. Mostfossil canids were found in Chile, Ecuador, Bolivia, Brazil, Venezuela and Argentina and are scarce or absent in othercountries. From Uruguay only fossils referred to Dusicyon gymnocercus, ‘Pseudalopex’ and ‘Canis’ are currently known.We describe new records that belong to large canids from the Sopas Fm. (Late Pleistocene) of Uruguay and discuss theirbiogeographic and paleoecologic relevance. These specimens are referred to Protocyon troglodytes and D. avus by means ofdescriptive and multivariate analysis and constitute the first records of these taxa for Uruguay, expanding and completingtheir distribution in the Late Pleistocene of South America. Both species could have been occupied ‘niches’ not representedby the carnivores previously registered in the Sopas Fm. (Puma concolor, Panthera onca, Lontra longicaudis, etc.)suggesting more complex biotic interactions in the mammalian assemblages than previously assumed. The largehypercarnivorous canid P. troglodytes could hunt medium-large sized mammals, pursuing their prey in packs over longdistances, while the medium canid D. avus could prey on small and middle mammals. Fil: Prevosti, Francisco Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Ubilla, M.. Universidad de la República; Uruguay Fil: Perea, D.. Universidad de la República; Uruguay