The dire wolf (Aenocyon dirus, "terrible wolf") is an extinct canine. It is one of the most famous prehistoric carnivores in North America, along with its extinct competitor Smilodon. The dire wolf lived in the Americas and eastern Asia during the Late Pleistocene and Early Holocene epochs (125,000–9,500 years ago). The species was named in 1858, four years after the first specimen had been found. Two subspecies are recognized: Aenocyon dirus guildayi and Aenocyon dirus dirus. 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 the plains, grasslands, and some forested mountain areas of North America, the arid savanna of South America, and the steppes of eastern Asia. 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 reports 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. However, the 2020 discovery of dire wolf fossils in north-east China indicates that dire wolves had crossed Beringia when it existed.
The dire wolf was about the same size as the largest modern gray wolves (Canis lupus): the Yukon wolf and the northwestern wolf. 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, and in North America its prey are known to have included western horses, ground sloths, mastodons, ancient bison, and camels. Its extinction occurred during the Quaternary extinction event 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. Dire wolves lived as recently as 9,500 years ago, according to dated remains.
