The small mammal assemblages from Alto de Ballester 1 and 2 in the Rubielos de Mora basin represent a unique faunal assemblage from the late early Miocene (Ramblian, MN 3). Together, the assemblages yielded five species of rodents (Peridyromys murinus, P. aff. murinus, P. aquatilis, Pseudotheridomys aff. fejfari and cf. Steneofiber depereti), and nine insectivores (Galericinae indet., Desmanella fejfari, Myxomygale minor, Desmanodon daamsi, Chainodus cf. sulcatus, Heterosorex sp., cf. Oligosorex thauensis, cf. Clapasorex alvarezae, and Paenelimnoecus cf. truyolsi). High abundance and diversity of insectivores, and the presence of a beaver and a dimylid show that the assemblages represent a humid, forested environment. This is in line with the palaeobotanical evidence of the basin. The two Alto de Ballester assemblages, which are very different from other Ramblian faunas, show that there was a variety of ecosystems on the Iberian Peninsula at this period, probably drier in the inland and more humid near the coastal zone.

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