The European record of the gerbil Myocricetodon (Rodentia, Mammalia) and its bearing on the Messinian salinity crisis

The gerbillid Myocricetodon is mainly known from the Miocene of Africa and Asia, but some small samples of this genus have been identified in southwestern Europe, interpreted as immigrants driven by the Messinian Salinity Crisis. However, the specific determination of these European populations and their relationships with African forms have proved controversial. The population from Negratín-1 (Guadix Basin, southern Spain) was attributed to the African species Myocricetodon jaegeri, but other European samples have still not been determined at the specific level. Here we describe the material of Myocricetodon from Almenara-M (eastern Spain), which represents the most abundant sample of the genus known from Europe, confirming its assignation to M. jaegeri. We also analyze material from Salobreña, Pino Mojón (southern Spain) and Castelnou-3 (southern France), concluding that these samples belong to the same species. The presence of these coeval and conspecific populations of Myocricetodon is explained by a single migratory event from northern Africa. The occurrence of Myocricetodon, interpreted as an indicator of warm and arid conditions, is restricted to southern and eastern Spain and the southeastermost extreme of France, being mainly limited to the Mediterranean coast. It is absent in other Iberian areas, such as the Granada, Cabriel and Teruel basins, despite their rich and well-studied record of late Miocene mammals. This distribution suggests the existence of different environmental (more humid) conditions in those areas during the latest Miocene, as already proposed for the Granada Basin. Our data also indicate that the presence of Myocricetodon in Europe was limited to a short interval close to the Miocene-Pliocene boundary, contrarily to other gerbils, namely Debruijnimys, which persisted during the Pliocene. This suggests that Myocricetodon could be extremely sensitive to environmental factors and its occurrence in Europe was linked to a specific moment of arid conditions.