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[EN] Geometric morphometric allows characterizing complex morphologies in order to quantify the geometry of the structure and facilitate comparisons. It allows performing methods analysing differentiation pattern based on variance, such as the Principal Component Analysis (PCA). For that reason, it has been chosen as the method to analyse the mandibles of two extinct species of cricetids rodents: Cricetodon aff. aureus and Megacricetodon minor from the MN6, middle Miocene from Goldberg and Steinberg (Germany). We performed a digitisation of 18 landmarks that includes the most relevant characteristics of these mandibles. We also performed a measure of the mechanical advantage and potential of the mandibles. In that way, we have been able to quantify notorious morphological differences on the angular and condylar processes and the lower masseter insertion and establish significant differences among the biomechanical behaviour of the mandibles. Later, we can relate the morphological and biomechanical information with speed and force biting., [ES] La morfometría geométrica permite caracterizar formas completas para cuantificar la geometría de la estructura y facilitar las comparaciones. Permite llevar a cabo metodologías que analizan esos patrones de diferenciación como el Análisis de Componentes Principales (ACP), a través del cual se estudia la varianza de una manera simple. Por esta razón ha sido el método elegido para analizar las mandíbulas de dos especies extintas de cricétidos: Cricetodon aff. aureus y Megacricetodon minor de la MN6, Mioceno medio de los yacimientos de Goldberg y Steinberg (Alemania). Hemos llevado a cabo la digitalización de 18 puntos de referencia (landmarks) que resumen las características más relevantes de las mandíbulas. Además hemos realizado la medición de las ventajas y potencias mecánicas de estas. De esta manera, hemos podido cuantificar diferencias morfológicas notorias en los procesos angular y condilar y en la inserción del masetero inferior y establecer diferencias significativas entre los comportamientos biomecánicos de las mandíbulas para después relacionarlo con la velocidad y la fuerza de la mordida de estos roedores.

The maxillary presented in this work has been excavated in the middle Miocene karst filling Petersbuch 136 (Germany, Bavaria) and shows the oldest evidence of dental anomaly in a sciurid. The aberrant morphology, probably hyperdontia or no replacement of roots of deciduous teeth, affects the area of the P3, a tooth that is generally not well documented in the Spermophilinus record.

Karydomys is a rare and little diversified democricetodontine, of which only six species are currently recognized. This group of rodents is first recorded in the early Miocene (MN3) in China and spread quickly thereafter to Kazakhstan and Greece (MN4). Karydomys reached south-western and central Europe by early middle Miocene times (MN5), from where it became extinct shortly thereafter (MN6). A new species of Karydomys is here described from the Miocene Keramia Formation of Chios Island (north-eastern Aegean Sea). Karydomys strati sp. nov. is characterized by the presence of a labial spur on the anterolophule, the lack of anterior protolophule on the M1 and by the presence of a double metalophule on the M2. A cladistics analysis involving all the species of Karydomys and some closely related species of Democricetodon and Cricetodon show that Karydomys split early into two different lineages, an ‘eastern stock’, which includes the central Asian (K. debruijni and K. dzerzhinskii) and Greek (K. symeonidisi, K. boskosi and K. strati) species, and a ‘western lineage’ comprising the western and central European species (K. wigharti and K. zapfei). The evolutionary stage of Karydomys strati suggests that the lowermost part of the Keramia Formation, usually attributed to the middle Miocene, is older than previously thought.

Simplomys, a dormouse with a simple dental morphology compared to other glirids, shows a continuous evolution in Spain during the end of the Ramblian and up to the middle Aragonian, the stratigraphic frame considered in this work. In contrast, the record of the genus in Central Europe is reduced to a few localities spanning from the early to the middle Miocene. We review the record from the Burdigalian to Langhian equivalent to the deposition of the uppermost Upper Marine Molasse (OMM) to the lower part of the Upper Freshwater Molasse (OSM) and conclude the occurrence of three distinct species. The youngest species, Simplomys simplicidens, is recognised in Schönenberg (Germany, MN5) and Courrendlin-Solé (Switzerland; MN4). Material from a fissure filling near Glovelier (Switzerland, MN4) supplied the new species, Simplomys hugi, whereas the localities Petersbuch 2 and Erkersthofen 2 (both fissure fillings from Germany, MN4) contain species closely related to it. Finally, and pending further advances in the taxonomy of the Iberian Simplomys, the oldest population from the fissure filling of Schnaitheim (Germany; MN3) remains in open nomenclature (Simplomys sp.). The genus Simplomys has not been recorded eastwards from the Swabian and Franconian Jura Plateaus from Germany and its youngest occurrence in Schönenberg is correlated to the South German local scale OSM C+D, at around 15.5 Ma.