Cranial and mandibular morphology of Middle Pleistocene cave bears (<i>Ursus deningeri</i>): implications for diet and evolution

Deninger’s bears (<i>Ursus deningeri</i>) have been studied less frequently than <i>Ursus spelaeus</i> <i>s.l.</i> Our objective is to present, for the first time, an analysis of the skull shape of <i>U. deningeri</i>. Bear crania and mandibles were digitised with a Microscribe or CT-scanned and the surface models subsequently landmarked. The landmarks were chosen based on a compromise between functional morphology and sample size. Results show that <i>U. deningeri</i> and <i>U. spelaeus</i> mandibles display very similar morphologies and allometric trajectories, both to each other and to <i>Ailuropoda melanoleuca</i>. It is inferred that masticatory adaptations to a herbivorous diet were already present in the Middle Pleistocene. <i>U. deningeri</i> displays a cranial morphology that is similar to that of <i>U. spelaeus</i> when comparing all species, but <i>U. deningeri</i> has a relatively narrower and dorsoventrally lower zygomatic arch than <i>U. spelaeus</i>, although the masticatory signal is less strong in the skull. We observe intraspecific differences between different populations of <i>U. deningeri</i>, which could parallel the genetic diversity found in <i>U. spelaeus</i>. The intraspecific differences found within <i>U. deningeri</i> may be temporal and/or geographical in nature and could be related to the evolution of the Late Pleistocene cave bear, but this hypothesis remains to be tested.