The phylogenetic descent of the extant wolf C. lupus from C. etruscus through C. mosbachensis is widely accepted. The earliest fossils of C. lupus were found in what was once eastern Beringia at Old Crow, Yukon, Canada, and at Cripple Creek Sump, Fairbanks, Alaska. The age is not agreed upon but could date to one million years ago. Considerable morphological diversity existed among wolves by the Late Pleistocene. They had more robust skulls and teeth than modern wolves, often with a shortened snout, a pronounced development of the temporalis muscle, and robust premolars. It is proposed that these features were specialized adaptations for the processing of carcass and bone associated with the hunting and scavenging of Pleistocene megafauna. Compared with modern wolves, some Pleistocene wolves showed an increase in tooth breakage that is similar to that seen in the extinct dire wolf. This suggests that they either often processed carcasses, or that they competed with other carnivores and needed to consume their prey quickly. Compared with those found in the modern spotted hyena, the frequency and location of tooth fractures found in these wolves indicates that they were habitual bone crackers.