Arctodus

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Arctodus, also known as the Short-Faced Bear, is a genus of extinct bear. One species, the Giant Short-Faced Bear (Arctodus simus), is believed to be the largest bear that ever lived. Standing 5.5 feet at the shoulder (over 11 feet when standing on hind legs) and equipped with powerful jaws this bear would have been an intimidating sight. From the fossils found, Giant short-faced bear was estimated to weigh 2000 pounds (900 kg) However, it was leaner in build than the Brown Bear.

Arctodus seems to have been an omnivore, as the jaw structure and teeth resemble those of the modern bears, but with a bias toward eating much more meat than do modern bears. It was, by far the biggest land predator during the Ice Age in North America. It may have attacked bison, deer, elk, camel and other large herbivores, but probably partly lived, like many other large carnivores like lions, as a scavenger. Compared to modern brown bears it had much longer limbs and was generally more slender. It had a very short, broad muzzle which gives rise to its name, and which gave it a very powerful bite. Its long legs were adapted for a faster running-style than modern bears. This trait enabled Arctodus to range far and wide in search of prey and carrion, while its powerful bite enabled it to crack open bones to reach rich marrow.

The largest known skull of Arctodus was found by a Yukon gold miner. Another fossil from southern Saskatchewan indicates that Arctodus lived there more than 70,000 years ago. Arctodus simus, the largest species, ranged the high grasslands of western North America from Alaska to Mexico, while a lighter-built species (Arctodus pristinus) with smaller teeth inhabited the more heavily wooded Atlantic coastal region.

The short-faced bear belongs to a group of bears known as the Tremarctine bears, which are of New World origin. The earliest member of the Tremarctinae is Plionarctos, which lived in Texas during the Pliocene Epoch (about 5-2 million years ago). It is likely that this genus is ancestral to the Spectacled Bear (Tremarctos) and the short-faced bear. Although the early history of Arctodus is poorly known, it evidently became widespread in North America by the Kansan age (about 800,000 years ago).

The short-faced bear became extinct some 12,000 years ago, perhaps partly because some of its large prey died out earlier, and partly because of competition with the smaller, more herbivorous brown bears that entered North America from Eurasia. Since its demise coincides with the development of the Clovis technology and improved hunting techniques by humans in North America, hunting may also have contributed to its extinction both directly and due to the depletion of other large mammals on which it depended for food.

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• An artist's impression of Arctodus