The dire wolf (Aenocyon dirus) is an extinct canine that lived in the Americas (with a possible single record also known from East Asia).
Dire wolf lived in the late Pleistocene to the early Holocene (125,000–9,500 years before present or YBP) in North and South America.
In North America they lived as recently as 9,440 years ago, according to dated remains.
In 2021, a DNA study found the dire wolf to be a highly divergent lineage when compared with the extant wolf-like canines, so it was assigned genus Aenocyon (Ancient Greek: "terrible wolf").
Two subspecies are recognized, these being Aenocyon dirus guildayi and Aenocyon dirus dirus.
It is one of the most famous prehistoric carnivores in North America, along with its extinct competitor, the sabre-toothed cat Smilodon fatalis.
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, and in the arid savannah of South America.
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).
The largest northern wolves today have a shoulder height of 38 in (97 cm) and a body length of 69 in (180 cm). Some dire wolf specimens from Rancho La Brea are smaller than this, and some are larger.
A study of isotope data of La Brea dire wolf fossils dated 10,000 YBP provides evidence that the horse was an important prey species at the time, and that sloth, mastodon, bison, and camel were less common in the dire wolf diet.
This indicates that the dire wolf was not a prey specialist, and at the close of the late Pleistocene before its extinction it was hunting or scavenging the most available herbivores.
The large size of the dire wolf provides an estimated prey size in the 300 to 600 kg (660 to 1,320 lb) range.
When compared with the dentition of genus Canis members, the dire wolf was considered the most evolutionary derived (advanced) wolf-like species in the Americas.
A study of the estimated bite force, when adjusted for the body mass, found that bite force of the canines (in newtons/kilogram of body weight) was greatest in the dire wolf.
A. d. guildayi is the most common carnivoran found at La Brea, followed by Smilodon. Remains of dire wolves outnumber remains of gray wolves in the tar pits by a ratio of five to one.
The many A. d. guildayi and Smilodon remains found in the tar pits suggests that both were social predators.
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.
Another cause of the extinction of dire wolf, although debated, is the competition with other species including overexploitation by newly arrived human hunters.

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