Pleistocene Asian black bear (Ursus thibetanus Cuvier, 1823) in the Iberian Peninsula: new evidence and a complete review

The Asian black bear (Ursus thibetanus Cuvier, 1823) is a medium-sized ursid that currently mostly inhabits environments of dense foliage and forests in southern and eastern Asia. This species is currently extinct in Europe, but during the Middle Pleistocene and the beginning of the Late Pleistocene its distribution was wider and reached until Southern Siberia, the Ural Mountains, Caucasus and western Europe. The main objective of this work is to provide a detailed description of all the Ursus thibetanus remains from the Iberian Peninsula, describing for the first time the new remains, and discuss the chronological framework of the presence of this taxon in the largest of the southern European peninsulas. The Iberian Peninsula has yielded paleontological evidence of this taxon in five sites (Bolomor, Koskobilo, La Llanera, Cau d'en Borràs and Villavieja), and we present new paleontological evidence from the latter three sites, which is important due to the scarcity of U. thibetanus fossil remains. We compare the morphology of these new remains with both European Pleistocene fossils and recent U. thibetanus. Up until recently, its distribution in Iberia was thought to be restricted to the East of the Iberian Peninsula. But the recent identification of U. thibetanus remains in Koskobilo (Navarre) and in La Llanera (Oviedo) has resulted in a wider distribution of this species than what was previously thought. The dental remains from Koskobilo, La Llanera, Villavieja, Bolomor and Cau d'en Borràs fit well within the Pleistocene U. thibetanus from Europe morphologically and metrically. Some Iberian remains are morphologically similar to previously described U. thibetanus Pleistocene fossil subspecies. A M2 from Bolomor is morphologically closer to U. t. mediterraneus (MIS 7), and a M2 from Koskobilo is similar to U. t. kurteni (MIS 6-7). The postcranial fossil remains from Cau d'en Borràs and Villavieja fit well within the recent U. thibetanus range of variation. Except for the remains from Bolomor (MIS 5e and MIS 7), the rest of the Iberian U. thibetanus fossils are difficult to ascribe chronologically. Based on other biochronological proxies, Cau d'en Borràs and Koskobilo can tentatively be assigned to the MIS 7-5 range, Villavieja could be assigned to MIS 13-5, and La Llanera is probably the oldest record of U. thibetanus in Iberia (MIS 15-13). However, until new direct datings are performed on the sites, the proposed chronologies should be regarded with caution.