Evolution and Morphological Variability of Cheek Teeth in the Kudaro Cave Bear (Ursus kudarensis, Carnivora, Ursidae)

The variability of cheek teeth over time was studied with the use of univariate and multivatiate statistical analyses for 1370 tooth specimens of the Kudaro cave bear (Ursus kudarensis) (Baryshnikov 1985) collected in the Kudaro 1 and Kudaro 3 caves in the Caucasus. The material examined included two chronosubspecies: U. k. praekudarensis (middle part of the Middle Pleistocene, nearly 350 000 years ago) and U. k. kudarensis (Late Pleistocene, nearly 120 000-40 000 years ago), as well as a sample of intermediate stratigraphic position referred to as a transitional form (the end of the Middle Pleistocene, nearly 250 000 years ago). Our study detected no single pathway of evolutionary change in the cheek teeth of U. kudarensis, instead showing specific modifications for the premolars, molars, and even individual teeth (e.g., m3) in the context of high individual variability. In size, the teeth of U. k. praekudarensis occupied an intermediate position between the more robust teeth of the transitional form and the smaller teeth of U. k. kudarensis. By the range of morphometric characters (size and crown proportions), the transitional form was more closely related to U. k. kudarensis than to U. k. praekudarensis. At the same time, the parameters of allometric variation of the transitional form either related it to U. k. praekudarensis or were of the original nature. The calculated rate of evolution of the metric characters was found to be dissimilar not only for different teeth but also for different measurements of the same tooth crown, and these modifications themselves were oppositely directed. A comparison with the main evolutionary trends in European cave bears revealed the unique, independent character of evolution of the cheek teeth in the Kudaro cave bear, which is expressed to different degrees for the upper and lower rows of teeth.