Loss of megafauna, an aspect of defaunation, can precipitate many ecological changes over short time scales. We examine whether megafauna loss can also explain features of lasting ecological state shifts that occurred as the Pleistocene gave way to the Holocene. We compare ecological impacts of late-Quaternary megafauna extinction in five American regions: southwestern Patagonia, the Pampas, northeastern United States, northwestern United States, and Beringia. We find that major ecological state shifts were consistent with expectations of defaunation in North American sites but not in South American ones. The differential responses highlight two factors necessary for defaunation to trigger lasting ecological state shifts discernable in the fossil record: (i) lost megafauna need to have been effective ecosystem engineers, like proboscideans; and (ii) historical contingencies must have provided the ecosystem with plant species likely to respond to megafaunal loss. These findings help in identifying modern ecosystems that are most at risk for disappearing should current pressures on the ecosystems' large animals continue and highlight the critical role of both individual species ecologies and ecosystem context in predicting the lasting impacts of defaunation currently underway. megafauna | extinction | Quaternary | North America | South America D efaunation is occurring at a rapid pace presently (1-3).Losses are particularly severe for megafauna (1) (considered here as animals with an average body size ≥44 kg), whose removal can trigger the following: changes in vegetation structure and species composition; reductions in environmental heterogeneity, species richness, evenness, seed dispersal, nutrient cycling and distribution, and ecosystem services; coextinction of dependent species; and increases in disease-transmitting organisms (1, 4-14) and fire frequency and/or intensity (15-17).Most work on defaunation has been in contemporary ecosystems. Much less is known about how it manifests over millennial time scales. A natural experiment to assess lasting effects of megafauna loss is provided by the extinctions of late-Quaternary megafauna in the Americas, part of global-scale ecological state shift (18), during which about half of the world's large-bodied mammal species (19,20) disappeared. In North America, ∼60 megafaunal species died out, with the youngest occurrences of dated species typically falling between ∼13,000 and 11,000 y ago (19). In South America, ∼66 species were lost over a longer time span (21-23).With a few important exceptions (6, 17, 24-29), the major changes in vegetation and mammalian community structure that accompanied Quaternary extinctions have been interpreted as responses to changing climate (17-19, 21, 23, 25-27, 29-35). Here, we build on recent work of paleoecologists (17,25,28,29,32,36) and ecologists (1, 3-7, 9, 10, 15, 16, 37) ApproachThe late-Quaternary impact of losing 70-80% of the megafauna genera in the Americas (19) would be expected to trigger biotic transitions that would b...

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New detrital zircon U-Pb geochronology data from the Cenozoic Magallanes-Austral Basin in Argentina and Chile ~51°S establish a revised chronostratigraphy of Paleocene – Miocene foreland synorogenic strata and document the rise and subsequent isolation of hinterland sources in the Patagonian Andes from the continental margin. The upsection loss of zircons derived from the hinterland Paleozoic and Late Jurassic sources between ca. 60-44 Ma documents a major shift in sediment routing due to Paleogene orogenesis in the greater Patagonian-Fuegian Andes. Changes in the proportion of grains from hinterland thrust sheets, comprised of Jurassic volcanics and Paleozoic metasedimentary rocks, provide a trackable signal of long-term shifts in orogenic drainage divide and topographic isolation due to widening of the retroarc fold-thrust belt. Youngest detrital zircon U-Pb ages confirm timing of Maastrichtian – Eocene strata, but require substantial age revisions for part of the overlying Cenozoic basinfill during the late Eocene and Oligocene. The upper Río Turbio Formation, previously mapped as middle to late Eocene in the published record, records a newly recognized latest Eocene-Oligocene (37-27 Ma) marine incursion along the basin margin. We suggest that these deposits could be genetically linked to the distally placed units along the Atlantic coast, including the El Huemul Formation and the younger San Julián Formation, via an eastward deepening within the foreland basin system that culminated in a basin-wide Oligocene marine incursion in the Southern Andes. The overlying Río Guillermo Formation records onset of tectonically generated coarse-grained detritus ca. 24.3 Ma and a transition to the first fully nonmarine conditions on the proximal Patagonian platform since Late Cretaceous time, perhaps signaling a Cordilleran-scale upper plate response to increased plate convergence and tectonic plate reorganization.

Se presenta una lista actualizada de los mamíferos vivientes con registros en Chile, compilada en diciembre de 2020. La lista incluye 163 especies silvestres agrupadas en 85 géneros, 31 familias y ocho órdenes. De estas especies, 20 son endémicas del país. También se provee la lista de 22 especies exóticas con poblaciones silvestres en Chile. Dado que aún persisten áreas de Chile que no han sido suficientemente exploradas, al tiempo que varios géneros no han sido adecuadamente revisados, y debido a que el estatus de algunas formas nominales es debatido, avizoramos que esta lista deberá ser actualizada en el futuro cercano.

The description of an I 3 assigned to Arctotherium sp. obtained from the Baño Nuevo-1 site (Central Patagonia, Chile) is presented. The finding was recovered from Layer 5 and it is associated to Macrauchenia sp., Lama guanicoe, Felidae, Camelidae, Equidae and Mylodontidae, within a sterile deposit of cultural material, dated between ca. 13.500 and 11.200 BP. Despite the fact that it is only a single specimen, such finding extends the known distribution for the genus in Chile.