The Dire Wolf (Canis dirus) is an extinct carnivorous mammal of the genus Canis, and was most common in North America and South America during the Pleistocene. Although it was closely related to the Gray Wolf, it was not the direct ancestor of any species known today. Unlike the Gray Wolf, which is of Eurasian origin, the Dire Wolf evolved on the North American continent, along with the Coyote. The Dire Wolf co-existed with the Gray Wolf in North America for about 100,000 years.
The Dire Wolf was 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.
The dire wolf was slightly larger than the grey wolf, averaging about 1.5 metres (5 ft) in length and weighing about 57-79 kilograms (125-175 lb). Despite superficial similarities to the grey wolf, there were significant differences between the two species
. The legs of the dire wolf were proportionally shorter and sturdier than those of the grey wolf, and its brain case was much smaller.
The dire wolf's teeth were similar to the grey wolf's, only slightly larger. Many paleontologists have proposed 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. The upper carnassials
had a much larger blade than that of the grey wolf, indicating greater slicing ability. It had a longer temporal fossa
and broader zygomatic arches
, indicating the presence of a large temporalis muscle
capable of generating slightly more force than a grey wolf's. However, other scientists have noted that the dorsoventral and labiolingual force profiles are indistinguishable from those of other canids such as coyotes
and African wild dogs
, indicating a similar diet. Dire wolf teeth lacked the craniodental adaptations of habitual bonecrushers such as hyenas
. The dorsoventrally weak symphyseal region
indicates it killed in a manner similar to its modern relatives, by delivering a series of shallow bites, strongly indicating pack hunting behaviour. However, the incidence of broken post-carnassial molars is much higher than in fossil grey wolves, indicating that the species was probably less adapted to bone crushing than the grey wolf.
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 became the ancestors of modern wolves, jackals, foxes
, and the Raccoon Dog
. By , canids had spread to Africa
) and South America
(Late Pliocene). Their invasion of South America as part of the Great American Interchange
was enabled by the formation of the Isthmus of Panama
3 Ma ago.
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 on 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 relict population in the Ozark mountains as recently as 4,000 years ago.
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
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 of Natural Sciences 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.
- Clark Kimberling 1996, "David Dale Owen and Joseph Granville Norwood: Pioneer Geologists in Indiana and Illinois," Indiana Magazine of History 62 (March 1996), Indiana University, pages 2-25.