Late Aragonian mammal sites of Cuesta del Rey (Duero Basin, Burgos, Spain)

The Cuesta del Rey mammal sites located on the NE border of the Duero Basin are of great importance with regard to understand the general biostratigraphy of the basin, because Miocene mammal sites are extremely scarce in this area in comparison with the central part of the basin. The mammals identifi ed in Cuesta del Rey-1 are: Eulipotyphla: cf. Miosorex sp.; Rodentia: Heteroxerus sp., Armantomys cf. tricristatus, Megacricetodon ibericus, Megacricetodon minor-Megacricetodon debruijni, Hispanomys sp. and Democricetodon sp. The Cuesta del Rey-1 rodent assemblage is characteristic of the end of the upper Aragonian (MN 7/8, end of the middle Miocene), equivalent to the local subzone G3 of the G zone. The presence of the genera Heteroxerus and Armantomys, and the predominance of Megacricetodon (with 80% of the total percentage of the minimum number of individuals of the micromammals) suggested an open savannah or steppe palaeoenvironment. The mammals identifi ed in Cuesta del Rey-3 are: Rodentia: Megacricetodon cf. ibericus; Artiodactyla: Dorcatherium sp. and Listriodon cf. splendens. Dorcatherium sp. represents the fi rst appearance of the Tragulidae family in the Duero Basin, suggesting the existence of permanent watercourses.