Paleocaves exhumed from the Miramar Formation (Ensenadan Stage-age, Pleistocene), Mar del Plata, Argentina

Exhumed organic megastructures are analyzed in this paper. Large paleocaves (0.7-2.1 m width and 0.7-1.5 m height) are related to the digging of Xenarthra (Mammalia) that lived in the Pampas during the Pleistocene. Some of these burrows are completely filled by sediment, and others are found partially empty. They occur within the city of Mar del Plata and its surroundings, mostly restricted to the Miramar Formation. Three types of galleries have been identified. The larger caves (type I) are related to the digging activity of mylodontids (e.g. Glossotherium). Type II caves are related to smaller mylodontids (Scelidotherim leptocephalus). Other caves of similar size are attributed to the dasypodid Pampatherium (type III). The number of digits recognized in scratch marks on the cave walls helped to distinguish between mylodontid and dasypodid activities. The abundance of these caves has been interpreted in relation to water availability in the surroundings of the Tandilia Range, flooding potential, and shelter to avoid predation by carnivores. The paleobiologic and paleoecological significance of the structures assigned to ants or termites, and cave reoccupation by specimens of Arctotherium latidens (Ursidae, Tremarctinae), are also discussed. (C) 2009 Elsevier Ltd and INQUA. All rights reserved.