Cranial morphological differences within U. deningeri - U. spelaeus lineage: A double traditional and geometric morphometrics approach

Two complete skulls of Ursus deningeri, one recovered from the Middle Pleistocene site of the Sima de los Huesos in the Sierra de Atapuerca (Spain), and the other one from Petralona (Chalkidiki, Greece), were reconstructed through computed tomography. The cranial morphology of U. deningeri was analysed using dual “traditional” and geometric morphometric and compared to extinct and extant Ursidae (Ursus spelaeus, Ursus arctos, and Ursus americanus). The goal of this work was to explore the variation in skull morphology between these different taxa. The analysis presented here indicates that combined traditional and geometric morphometric methods could be useful for a taxonomic approach. In this preliminary study, in which only 2D information is used, it is possible to distinguish the three bear lineages presented here. U. deningeri occupies an intermediate position between the U. spelaeus and U. arctos, which supports an early evolutionary stage of U. deningeri within the cave bear phylogenetic lineage. This study establishes that genera of the Ursus can be differentiated based on cranial shape. Combined studies with computed tomography, traditional and geometric morphometrics of endocraneal remains will provide important new evidence about diet, taxonomical and biochronological studies.