Craniometrical variability in the cave bears (Carnivora, Ursidae): Multivariate comparative analysis

Morphological and molecular data suggest the existence of several taxa of cave bears, which were found to belong to three major mitochondrial haplogroups: kudarensis (kudarensis), spelaeus (ladinicus, eremus, spelaeus), and ingressus (uralensis, ingressus, kanivetz). An analysis of craniometrical variability was carried out based on 20 measurements of 279 skulls from 40 European, Ural, and Caucasian localities, in order to investigate morphological similarity/dissimilarity of these taxa in a multivariate approach. The craniometrical analysis divides cave bears into two groups: small cave bears and large cave bears. The group of small bears consists of rossicus/uralensis and ladinicus. In some skull proportions, these taxa display intermediate position between brown and cave bears, i.e. presumably possessing archaic characters of their common ancestor. The group of large bears includes taxa with more specialized skulls. An early radiation within this group is demonstrated by kudarensis which probably ranged across Asia, and deningeri which occupied Europe east to the Ural Mountains. In its craniometrical characters, kanivetz from the Late Pleistocene of the Urals resembles deningeri. Other taxa of large cave bears (spelaeus, ingressus and eremus) reveal further evolution of cranial characters, being similar in the skull proportions. The level of difference between spelaeus and ingressus does not exceed that between subspecies of the recent brown bear, such as Ursus arctos beringianus and U. a. piscator. The examined isolated population of large cave bears from Volga River region (Zhiguli Hills) is similar to ingressus. Thus, based on the craniometrical data, the following species of cave bear are recognized: Ursus kudarensis (with the subspecies U. k. praekudarensis and U. k. kudarensis), U. deningeri (several subspecies), U. rossicus (with subspecies U. r. rossicus and U. r. uralensis), U. ladinicus, U. spelaeus (with subspecies U. s. spelaeus, U. s. eremus, U. s. ingressus, and, provisionally, U. s. kanivetz,).