Dire wolf
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The dire wolf (Aenocyon dirus ) is an extinct species of canine which was native to the Americas during the Late Pleistocene and Early Holocene epochs (125,000–10,000 years ago). The species was named in 1858, four years after the first specimen had been found. Two subspecies are proposed, Aenocyon dirus guildayi and Aenocyon dirus dirus, but this assignment has been recently considered questionable. The largest collection of its fossils has been obtained from the Rancho La Brea Tar Pits in Los Angeles. Dire wolf remains have been found across a broad range of habitats including plains, grasslands, and some forested mountain areas of North America and the arid savanna of South America. The sites range in elevation from sea level to 2,255 meters (7,400 ft). Dire wolf fossils have rarely been found north of 42°N latitude; there have been only five unconfirmed records above this latitude. This range restriction is thought to be due to temperature, prey, or habitat limitations imposed by proximity to the Laurentide and Cordilleran ice sheets that existed at the time. The dire wolf was about the same size as the largest modern forms of gray wolf (Canis lupus). A. d. guildayi weighed on average 60 kilograms (132 lb) and A. d. dirus was on average 68 kg (150 lb). Its skull and dentition matched those of C. lupus, but its teeth were larger with greater shearing ability, and its bite force at the canine tooth was stronger than any known Canis species. These characteristics are thought to be adaptations for preying on Late Pleistocene megaherbivores; in North America, its prey is suggested to have included western horses, dwarf pronghorn, flat-headed peccary, ground sloths, ancient bison, and camels. Dire wolves lived as recently as 10,000 years ago, according to dated remains. Its extinction occurred during the Quaternary extinction event, disappearing along with its main prey species; its reliance on megaherbivores has been proposed as the cause of its extinction, along with climatic change and competition with other species, or a combination of those factors.