Dental molds from: Three-dimensional dental topography and feeding ecology in the extinct cave bear

The cave bear (Ursus spelaeus s.l.) is an iconic extinct bear that inhabited the Pleistocene of Eurasia whose extinction causes are controversial. To identify the actual causes of the cave bear extinction, it is crucial to understand their feeding preferences. Here, we quantify shape descriptor metrics (DNE, RFI and OPCR) in three dimensional (3D) models of cave bear upper teeth (P4-M2) to make inferences on its controversial feeding behaviour. We use a comparative sample including representatives of all living bear species with known diets as a template. Our topographic analyses evidence that the complexity of upper tooth rows in living bears is more associated with the mechanical properties of the items consumed than with the type of food. Cave bears exhibit intermediate values on topographic metrics between those exhibited by the bamboo-feeder giant panda (Ailuropoda melanoleuca) and those taken by specialists in hard-mast consumption (Ursus arctos and Ursus thibetanus). The crown topography of cave bear upper teeth suggests a high efficiency to chew on tough vegetal resources of lower-quality, and no living bear is currently exploiting it. Our results align with a climatic-driven hypothesis to explain demise in cave bear populations during the late Pleistocene.

广义洞熊（Ursus spelaeus s.l.）是一类标志性的已灭绝熊类，曾分布于欧亚大陆的更新世时期，其灭绝原因至今尚存争议。为明确洞熊灭绝的真正诱因，解析其摄食偏好至关重要。本研究通过对洞熊上前齿（P4-M2）的三维（3D）模型量化其形状描述符指标（DNE、RFI与OPCR），以此推断其存在争议的摄食行为。本研究以食性明确的所有现生熊类类群作为对照参照样本。牙冠形貌分析结果表明，现生熊类的上牙列复杂度与所摄食物的机械特性关联更为紧密，而非食物类别。洞熊的形貌指标数值介于食竹大熊猫（Ailuropoda melanoleuca）与硬果实专食类群（棕熊Ursus arctos、亚洲黑熊Ursus thibetanus）之间。洞熊上前齿的牙冠形貌特征显示，其对低质坚韧植物资源具备极高的咀嚼效率，而当前现生熊类中并无类群利用此类资源。本研究结果支持“晚更新世洞熊种群灭绝由气候因素驱动”的相关假说。