Dire Wolf
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The Dire Wolf (Canis dirus) is an extinct member of the genus Canis (which contains the other wolves, the Coyote, jackals, and the other canines), and was most common in North America during the Pleistocene. Although it was closely related to the Gray Wolf, it was not the direct ancestor of any species known today. The Dire Wolf co-existed with the Gray Wolf in North America for about 100,000 years. They were one of the abundant Pleistocene megafauna???a wide variety of very large mammals that lived during the Pleistocene. Approximately 10,000 years ago, the Dire Wolf became extinct along with most other North American megafauna.

The first specimen of a Dire Wolf was found by Francis A. Linck at the mouth of Pigeon Creek along the Ohio River near Evansville, Indiana in 1854, but the vast majority of fossils recovered have been from the La Brea Tar Pits in California.

Characteristics
The Dire Wolf was larger than the Gray Wolf, the largest living wild canid. It averaged about 1.5 metres (5 feet) in length and weighed about 57-79 kilograms (125-175 pounds).

Despite superficial similarities in appearance, there were significant differences between the two species. The legs of the Dire Wolf were proportionally shorter and sturdier than those of the Gray Wolf, which suggests that the Dire Wolf was a poorer runner, and may have scavenged for food or hunted large, slower-moving prey.

The Dire Wolf had a larger, broader head and smaller brain-case than that of a similarly-sized Gray Wolf, and had teeth that were quite massive. Many paleontologists think that the Dire Wolf may have used its relatively large teeth to crush bone, an idea that is supported by the frequency of large amounts of wear on the crowns of their fossilized teeth. Dire Wolf skeletons have been found bearing healed and half-healed injuries similar to the ones found on modern wolves who have been injured while hunting large prey such as bison or horses. This suggests that the Dire Wolf also hunted for large, live prey.

Evolution and extinction
The fossil record suggests that the genus Canis diverged from the small, foxlike Leptocyon in North America sometime in the Late Miocene Epoch 9 to 10 million years ago (Ma), along with two other genera, Urocyon, and Vulpes. Canids soon spread to Asia and Europe (8 Ma) and become the ancestors of modern wolves, jackals, foxes, and the Raccoon Dog. By 4???5 Ma, canids had spread to Africa (Early Pliocene) and South America (Late Pliocene).

Over the next nine million years, extensive development and diversification of the North American wolves took place, and by the Mid-Pleistocene (800,000 years ago) Canis ambrusteri appeared and spread across North and South America. It soon disappeared from North America, but probably continued to survive in South America to become the ancestor of the Dire Wolf. (However there is some evidence to suggest that the Dire Wolf may have arisen from other small South American wolves.)

During the Late Pleistocene (300,000 years ago) the Gray Wolf (Canis lupus) crossed into North America via the Bering Strait land bridge. By 100,000 years ago the Dire Wolf also appeared in North America (probably from South America).

Starting about 16,000 years ago, coinciding with the end of the most recent Ice Age and the arrival of humans in North America, most of the large mammals upon which the Dire Wolf depended for prey began to die out (possibly as a result of climate and/or human-induced changes). Slower than the other wolf species on the continent at the time, primarily the Gray Wolf and Red Wolf, it could not hunt the swifter species that remained and was forced to subsist on scavenging. By 10,000 years ago, the large mammals and the Dire Wolf were extinct, although some fossils found in Arkansas suggest that they may have lived as a relic population in the Ozark mountains as recently as 4,000 years ago.

La Brea Tar Pits
The Dire Wolf is best known for its unusually high representation in the La Brea Tar Pits in California. In total, fossils from more than 3,600 individual Dire Wolves have been recovered from the tar pits, more than any other mammal species. This large number suggests that the Dire Wolf, like modern wolves and dogs, probably hunted in packs. It also gives some insight into the pressures placed on the species near the end of its existence.

Evansville Dire Wolf
The type specimen of the Dire Wolf was found in Evansville, Indiana in the summer of 1854, when the Ohio River was quite low. The specimen, a fossilized jawbone, was obtained by Dr. Joseph Granville Norwood from an Evansville collector named Francis A. Linck. Dr. Norwood, who at that time was the first state geologist of Illinois, sent the specimen to Joseph Leidy at the Academy of Natural Sciences of Philadelphia. Dr. Leidy determined that the specimen represented an extinct species of wolf and published a note to that effect in November 1854. In a publication dated 1858, Leidy assigned the name Canis dirus.

Dr. Norwood's letters to Dr. Leidy, as well as the type specimen itself, are preserved at the Academy in Philadelphia, although one of the letters indicates that the specimen was to be returned to Linck's family, as Linck himself died in August 1854.

Cultural References
Dungeons & Dragons employs the dire wolf as one of the monsters and further expands the selection to other animals such as dire apes and dire penguins.
Jerry Garcia wrote a song entitled "Dire Wolf", inspired by the tale of The Hound of the Baskervilles.
The dire wolf plays an important role through out George R.R. Martin's series A Song of Ice and Fire.
The Tragically Hip have a song called "The Dire Wolf" off their album "In Violet Light."

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