Bears of the Pleistocene

[brotherbear]

http://www.fs-media.net/kunden/ka/wp-con...rticle.pdf  
 
4 Conclusion In this study species separation was possible on the above listed postcranial elements of 2,295 specimens of Ursus deningeri and Ursus spelaeus, in contrast to some studies on dental material (GRANDAL D’ANGLADE & LÓPEZ-GONZÁLEZ 2004). Ursus spelaeus was distinguished by the shortened and narrowed humerus, radius and femur, also by a shrinkage of the elbow and knee joints. This meant a change in proportion of the proximal to the distal skeletal elements. Ursus deningeri shows shortening and narrowing mainly of the metapodials, especially of the metatarsals. The characteristics of Ursus deningeri and Ursus spelaeus which grew smaller during the course of time are interpreted as an allometric phenomenon, showing a negative correlation to body size. The species-separating differences are shown in these predominantly differing characteristic allometric features. Interestingly, species classification and factor extraction was possible especially with measurements of the proximal and distal joint surfaces. The mean values of the data sets analysed here also show that Ursus spelaeus was generally larger than Ursus deningeri. This is in accordance with present assumptions (EHRENBERG 1939, RABEDER 1989, RABEDER & HOFREITER 2004, SANTI et al. 2003). EHRENBERG’s assumption that Ursus spelaeus could not have been particularly specialized, more likely omnivorous (EHRENBERG 1962), was proven false by BOCHERENS using isotope analysis (BOCHERENS et al. 1994). Carnivorous food acquisition requires a higher degree of agility and mobility than is necessary for a purely herbivorous diet (PETRONIO et al. 2003). Leney associated pronounced gracility with a largely carnivorous diet and ungainliness with herbivory (GITTLEMAN ATHEN, K. Statistical analyses on skeletal elements of Ursus deningeri and Ursus spelaeus 158 1985, LENEY 2000). This supposition is reinforced both by the isotopegeochemical analyses of bone collagen from Ursus spelaeus and by the morphology of the molars. The weight-supporting elements were strengthened, especially the anterior extremities, which would have probably been used increasingly to dig for roots and other food. It may be that Ursus spelaeus´ diet was specialized on certain types of plants. The interpretation of the observations in this study is that the factor behind the differences, the cause, is a change in locomotion habits. This was associated with increased herbivory and a genetic change, possibly due to migration. It could be, that the ursids retreated south (southeast or southwest) and reimmigrated later in a more developed form. Climatic influence and subsequent changes in alimentation are also conceivable. The question of whether or not Ursus deningeri and Ursus spelaeus share a common genetic line was addressed by the discriminant analysis of the factor values. The results show a significant difference in only seven of the almost fifty different statistical operations. The interpretation of the data used in this study, is that the affiliation of Ursus deningeri and Ursus spelaeus is so close as to imply a common line of descent. The majority of 108 fossil finds, mostly from the old diggings from the Einhornhöhle points towards a dominance of the Ursus deningeri-morphology group. Findings from each species originated during a long time period. There are different explanations for this observation. The fossil finds probably accumulated over a long geological time span. Perhaps it was the period of time, when Ursus spelaeus relieved Ursus deningeri. Possibly the specimens show the transition interpretation according to Rabeder (VON KOENIGSWALD & HEINRICH 1999) or a local variety (RODE 1935) or another species, which wasn’t included in this study (RABEDER & HOFREITER 2004). Apparently the Einhornhöhle was, over a long time span, populated mainly by the geologically older Ursus deningeri, whose remains during the course of sedimentation became mixed with those of the younger Ursus spelaeus. Reply