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Sorex runtonensis (Mammalia, Soricidae) is a well-known Pleistocene taxon with a broad distribution in Europe. However, no record of the species had been reported from the Iberian Peninsula up to now. Here we present nearly two hundred specimens of S. runtonensis recovered from the Lower Red Unit (levels TE7-14) of Sima del Elefante (Sierra de Atapuerca, Burgos, Spain), dated to ~1.1-1.5 Ma. Rigorous morphometrical and morphological analyses allowed the assignation of the items from Sima del Elefante confidently to this taxon, distinguishing them from the several other Pleistocene species of similar size that inhabited Europe. Sorex runtonensis survived all through the Pleistocene (and maybe more), but the remains from Sima del Elefante exhibit some traits that appear to be particular to the Early Pleistocene, which agrees with the pre-Jaramillo chronology inferred for the lower levels of the site. Western Palearctic S. runtonensis has been regarded as a proxy of patchy and relatively arid, open past biotopes due to its similarity to recent Eastern Palearctic S. tundrensis. In light of this fact, and given the high relative quantities of this taxon at the site, previous palaeoenvironmental reconstructions proposed for the lowermost unit of Sima del Elefante should be revised to present a more ecologically diverse scenario than previously thought.

We have developed a protocol for reconstructing 3D models of the skulls of extinct species of small mammals. For the first time, the reconstruction uses fragments of fossils from a mixture of different specimens and from related extant species. We use free software and commercial computers to make the process reproducible and usable for the scientific community. We present a semi-quantitative protocol to face the problem of making 3D reconstructions of fossil species that are incomplete in the fossil record and/or represented by a mixture of different individuals, as usually occurs with small vertebrates. Therefore this approach is useful when no complete skull is available. The protocol combines the use of microCT scan technology with a subsequent computer treatment using different software tools for 3D reconstruction from microCT and 3D design and printing (e.g. Fiji, SPIERS, Meshlab, Meshmixer) in a defined order. This kind of free and relatively simple software, plus the detailed description, makes this protocol practicable for researchers who do not necessarily have great deal of experience in working with 3D. As an example, we have performed virtual reconstructions of the skulls of two species of insectivore small mammals (Eulipotyphla): Beremendia fissidens and Dolinasorex glyphodon. The resulting skulls, plus models of the extant shrews Blarina brevicauda, Neomys fodiens, Crocidura russula and Sorex coronatus, make it possible to compare characteristics that can only be observed by means of microCT 3D reconstructions, and given the characteristics of the material, using this protocol. Among the characters we can compare are the position of the mandibles, the spatial relations among all the teeth, the shape of the snout and, in general, all parameters related with the anatomy of the rostrum. Moreover, these reconstructions can be used in different types of context: for anatomical purposes, especially to see internal features or characteristics at whole-skull scale, for bioengineering, animation, or other techniques that need a digital model.

Se han medido 98 mandíbulas y 717 dientes de ejemplares de Sorex (Soricidae, Eulipotyphla) del Pirineo aragonés, navarro y vasco. El material, de la colección del Instituto Pirenaico de Ecología (IPE-CSIC), proviene de egagrópilas recogidas entre 1967 y 1969. Las muestras se han reclasificado utilizando criterios óseos morfológicos, biométricos y funciones discriminantes, resultando pertenecer a las especies Sorex minutus y Sorex coronatus. El estudio de S. coronatus es interesante ya que por su similitud con S. araneus y Sorex granarius se suelen confundir cuando sólo se cuenta con restos óseos y por tanto la información sobre cada especie en la península Ibérica y especialmente en Aragón es escasa. Por esta razón normalmente se agrupan ambas especies como Sorex sp. El análisis de las medidas muestra que hay una diferencia entre las poblaciones occidentales y las orientales del área estudiada. En general decrecen en tamaño mandibular hacia el oeste, y son más grandes en zonas con mayor influencia mediterránea que en las de influencia atlántica. Aunque las medidas más adecuadas para observar este fenómeno son las mandibulares, las medidas dentales permiten la comparación de los resultados con datos bibliográficos de material paleontológico, del que no se suelen conservar mandíbulas completas.