Evolution of cranio-dental features and distribution of brown bear (Ursus arctos L., 1758) in Europe.

The study of the fossil remains of the brown bear (Ursus arctos, L. 1758) of the Pleistocene has always been extremely interesting for the vertebrate paleontologists. The discovery of bear material in different sites (fluvio-lacustrine and cave deposits), and the study of the various ecological adaptations developed in conjunction with the speloid forms (Ursus deningeri Reichenau, 1906, Ursus spelaeus Rosenmǖller, 1794) has been crucial for the achievement of palaeoecological necessary schemes for the reconstruction of the European paleoterritory. However, most of the oldest specimens (Middle and Early Pleistocene), presents uncertain taxonomical attribution, making the origin and paleodistribution of the brown bear in Europe still unclear, just like its first occurrence in Italy (Azzaroli, 1983; Rabeder, Pacher, & Withalm, 2010; Wagner, 2010). Similarly, regarding the Late Pleistocene, the relative scarcity of fossil brown bear material in comparison with those of cave bear, and the poor presence of international scientific documentation, often make the morphological distinction between the two evolutionary lines very complicated, especially regarding the Italian territory. Currently, the brown bear is unequally distributed throughout Europe; in Italy two distinct populations are present, one in the Alps (Ursus arctos arctos L. 1758) and another which is endemic of the Central Apennine region (Ursus arctos marsicanus, Altobello 1921). The latter, given its peculiar morphological characteristics of the skull (similar to those of the speleoid forms), has been the subject of many studies. However, we do not have a clear framework about the dynamics of its isolation or its origin (Colangelo, et al., 2012; Meloro, Guidarelli, Colangelo, Ciucci, & Loy, 2017; Benazzo, et al., 2017). The work carried out during the thesis include: i) the census of the Italian and European material of U. arctos; ii) the analysis of most of the Italian and European fossil and sub-fossil specimens through the use of traditional methodologies (morphological description and biometric analysis); iii) the use of new technologies (axial tomography and digitization of the material through photogrammetry) applied to the analysis of two-dimensional and three-dimensional geometric morphometry. From the results obtained it has been possible to partially review the systematic position of the species U. etruscus, which would no longer be considered as common ancestor of both the arctoid and speloid lineages in Europe, (Zapfe, 1948; Mazza & Rustioni, 1994). Consequently, the arctoid form entered in Europe during various moments throughout the Quaternary, sharing the territory with U. deningeri first and U. spelaeus later. Other results show morphological patterns which allow to distinguish these two evolutionary lines, especially in the dental elements and in the brain, although some common features of the skull persist. Finally, from the study of the specimens from the central-southern Italian area, the first occurrence of U. arctos in Italy at Fontana Ranuccio (Lazio) has been highlighted, and the absence of U. arctos marsicanus features within the fossil record have been reported. Therefore, from the morphological analysis, the split between the two Italian populations should be occurred after the dating of the most recent site studied, the Gran Carro deposit (late Bronze Age / early Iron Age).