Fossil Cave Bear Rib Bone Group Pleistocene Period, 2.6 million years-11,700 years B.P. A group of three fossil cave bear rib bones from Ursus spelaeus. 87 grams total, 16-19 cm long (6 1/3-7 1/2 in.). From Romania. Acquired 1980s. Old Bristol collection. Ursus spelaeus became extinct at the beginning of the last Glacial Maximum, about 27,500 years ago. [3, No Reserve]