of wolves with similar skull and dentition have been found in western Beringia (northeast Siberia), the Taimyr Peninsula, the Ukraine, and Germany, where the European specimens are classified as Canis lupus spelaeusthe cave wolf. The Beringian wolves, and perhaps wolves across the mammoth steppe, were adapted to preying on now-extinct species through their unique skull and tooth morphology. This type of gray wolf that is adapted for preying on megafauna has been referred to as the Megafaunal wolf. It is possible that a panmictic (random mating) wolf population, with gene flow spanning Eurasia and North America, existed until the closing of the ice sheets, after which the southern wolves became isolated, and only the Beringian wolf existed north of the sheets. The land bridge became inundated by the sea 10,000YBP, and the ice sheets receded 12,000–6,000YBP. The Beringian wolf became extinct, and the southern wolves expanded through the shrinking ice sheets to recolonize the northern part of North America. All North American wolves are descended from those that were once isolated south of the ice sheets. However, much of their diversity was later lost during the twentieth century due to eradication. Description Olsen described the short-faced wolf skulls as follows: The Beringian wolf was similar in size to the modern Alaskan Interior wolf (C.l.pambasileus). The largest northern wolves today have a shoulder height not exceeding and a body length not exceeding . The average weight of the Yukon wolf is for males and for females. Individual weights for Yukon wolves can vary from to , with one Yukon wolf weighing . The Beringian wolves were also similar in size to the Late Pleistocene wolves whose remains have been found in the La Brea Tar Pits at Los Angeles, California. These wolves, referred to as Rancho LaBrea wolves (Canis lupus), were not physically different from modern gray wolves, the only differences being a broader femur bone and a longer tibial tuberositythe insertion for the quadriceps and hamstring musclesindicating that they had comparatively more powerful leg muscles for a fast take-off before a chase. The Beringian wolf was more robust, and possessed stronger jaws and teeth, than either Rancho LaBrea or modern wolves. During the Late Pleistocene, the more southerly occurring dire wolf (Canis dirus) had the same shape and proportions as the Yukon wolf, but the dire wolf subspecies C.dirusguildayi is estimated to have weighed on average , and the subspecies