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''Ursavus'' is an extinct genus of ursid carnivoran mammals that existed in North America, Europe, and Asia during the Miocene, living from about 23—5.3 million years ago (Mya), existing for roughly . It evolved from the bear-dog The genus apparently dispersed from Asia into North America about 20 Mya, becoming the earliest member of the subfamily Ursinae in the New World.〔Qiu Zhanxiang. 2003. Dispersals of Neogene Carnivorans between Asia and North America in Chapt 2, Bulletin of the American Museum of Natural History #279, pp18-31.〕 Qiu points out that if a questionable 29-million-year-old specimen of ''Ursavus'' reported in North America is validated, ''Ursavus'' may have evolved in North America and dispersed westward into Asia. The higher number of fossils in Europe grading toward eastern Asia make the westward dispersal unlikely. ''Ursavus'' was named by Schlosser (1899). It was assigned to the Ursidae by Schlosser (1899) and R. L. Carroll (1988); and to Ursavini by R.M. Hunt (1998) and Jin et al. (2007).〔〔R. L. Carroll. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Company, New York 1-698〕 In life, the various species would have been between cat-sized for the smaller species〔p 46〕 and wolf-sized for the larger members of the genus () and were mainly ground-dwelling omnivores or hypocarnivores. ''U. elmensis'', also known as the "dawn bear" is generally taken to be the earliest undisputed bear species.〔Derocher, A. E. & W. Lynch. 2012. Polar Bears: A Complete Guide to Their Biology and Behavior. The Johns Hopkins University Press, Baltimore〕 Currently, only ''U. orientalis'', from the Shanwang diatomite of Early Miocene China, is known from a complete skeleton.〔 However, ''U. orientalis'' may have been reassigned to the genus ''Ballusia'', thus is no longer considered part of ''Ursavus''. () Most other species are known from teeth and skull fragments. A complete skull has been found in the Gansu region of China () of a new species dubbed ''U. tedfordi''. From the late Miocene, it was about the size of a wolf and is believed to be nearest ancestor of most modern bear species apart from the giant panda and spectacled bear. ==Fossil distribution== Sites (not complete) and specimen ages: *Pawnee Buttes Site, Weld County, Colorado (''U. pawniensis'') ~23.03—5.3 Ma. *Shanwang diatomite, Shanwang, China (''U. orientalis''〔) ~17-16 Ma.〔 May belong to the genus Ballusia () *Pasalar site, Bursa, Turkey (''U. primaevus'') ~16—13.7 Ma. *Baigneaux-en-Beauc, Alsac, France (''U. brevirhinus'') ~16.9—16.0 Ma. *Hambach mine horizon 6C, Germany (''U. elmensis'') ~16.9—13.7 Ma. *Yost Farm Site, Saskatchewan, Canada (''U. primaevus'') ~16.3—13.6 Ma. *Myers Farm Site, Valentine Formation, Webster County, Nebraska (''U. brevirhinus'') ~16.3—13.6 Ma. *Lufeng site, Yunnan, China (''U. depereti'') ~7-6 Ma.〔 *Linxia Basin Gansu, China (''U. tedfordi'') ~9-7 Ma. () 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ursavus」の詳細全文を読む スポンサード リンク
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