Holocene mammals from Entre Ríos Province, Argentina. We present an unpublished collection of mammals from La Picada Formation (Holocene sensu lato) and San Guillermo Formation (upper Holocene) in the Entre Ríos Province, Argentina, deposited in the collection of the Museo de Ciencias Naturales y Antropológicas “Prof. Antonio Serrano’’ of Paraná City, Entre Ríos. Nine taxa were identified: Dusicyon avus (Carnivora: Canidae), Myocastor coypus (Rodentia: Echimyidae), cf. Hydrochoerus sp. (Rodentia: Caviidae), Dicotyles cf. D. tajacu (Cetartiodactyla: Tayassuidae), cf. Ozotoceros bezoarticus, Mazama sp. (Cetartiodactyla: Cervidae), Bos primigenius taurus (Cetartiodactyla: Bovidae), Equus ferus caballus (Perissodactyla: Equidae) and Cetartiodactyla indet. Ducysion avus and Dicotyles cf. D. tajacu are the first record of these taxa in Entre Ríos. The recognized rodents and cervids are commonly found in archaeological sites and in Quaternary units in Entre Ríos Province. Bos primigenius taurus and Equus ferus caballus are the first findings of post-Hispanic domestic taxa in Holocene sediments from Entre Ríos. The specimen from San Guillermo Formation is the first record of a vertebrate in this unit. Future multidisciplinary studies will be necessary in order to obtain more robust data that will allow us to elucidate the geological and faunistic recent past of the Entre Ríos Province. Keywords: Quaternary, fossils, South America, Argentinian Mesopotamia.

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