| Short-faced bears Temporal range: Middle to Late Pleistocene |
|
|---|---|
| A. simus from the La Brea tar pits | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Family: | Ursidae |
| Subfamily: | Tremarctinae |
| Tribe: | Tremarctini |
| Genus: | †Arctodus Leidy, 1854 |
| Species | |
|
|
Arctodus (Greek, "bear tooth") — known as the short-faced bear or bulldog bear — is an extinct genus of bear endemic to North America during the Pleistocene ~3.0 Ma.—11,000 years ago, existing for approximately three million years. Arctodus simus may have once been Earth's largest mammalian, terrestrial carnivore. It was the most common of early North American bears, being most abundant in California.[1]
Contents |
The short-faced bears belonged to a group of bears known as the tremarctine bears or running bears, which are endemic to North America and Europe. The earliest member of the Tremarctinae was Plionarctos edensis, which lived in Indiana and Tennessee during the Miocene Epoch, (10 mya). This genus is considered ancestral to Arctodus, as well as to the modern spectacled bear, Tremarctos ornatus. Tremarctos floridanus was a contemporary. 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).
A related group of bears are the South American genus Arctotherium, which reached similar size and short faced adaptions. They were also 10 feet tall on hind legs
Arctodus simus (2 to 1.9 Ma.), 110.2 kg (240 lb) and 800 kg (1,800 lb) as noted by Legendre and Roth, inhabiting a generally more northern and larger range. It was native to prehistoric North America from about 800,000 years ago, and became extinct about 12,500 years ago. It has been found from as far north as Ikpikpuk River, Alaska[2][3] to Lowndes County, Mississippi. It is one of the largest bears in the fossil record and was among the largest mammalian land predators of all time. The type specimen came from Potter Creek Cave in Shasta County, California.[4] Males from the Yukon region - the largest representatives of the species - would have stood about 1.80 m (5.9 ft) at the shoulder (on all fours), 4 m (13 ft) upright and may have weighed about 800 kg (1,800 lb).[5] Arctodus simus was the largest carnivorous mammal that ever lived in North America.
Arctodus pristinus (3 to 2.2 Ma.), a species with 2 specimens weighing 500.7 kg (1,100 lb) and 63.6 kg (140 lb)[6] inhabiting more southern areas from northern Texas to New Jersey in the east, Aguascalientes, Mexico[7] to the southwest, and with large concentrations in Florida, the oldest from the Santa Fe River 1 site of Gilchrist County, Florida paleontological sites.
A fossil of the South American giant short-faced bear (2 to 0.5 Ma.) species first found in 1935 in Argentina was re-examined in 2011, and found to be the largest bear to ever exist, weighing an estimated 1,600 kg (3,500 lb). The species was likely at least 3.4 m (11 ft) tall, and its humerus was similar in size to an elephant's.[8]
Researchers disagree on the diet of Arctodus. Analysis of Arctodus bones showed high concentrations of nitrogen-15, a stable nitrogen isotope accumulated by meat-eaters, with no evidence of ingestion of vegetation. Based upon this evidence A. simus was highly carnivorous, and as an adult would have required 16 kilograms (35.3 lb) of flesh per day to survive.[9][10]
One theory of its predatory habits envisions Arctodus simus as a brutish predator that overwhelmed the large mammals of the Pleistocene with its great physical strength. However, despite being very large its limbs were too gracile for such an attack strategy. Alternatively, long legs and speed (50–70 kilometres per hour (30–40 mph)) may have allowed it to run down Pleistocene herbivores such as steppe horses and saiga antelopes in a cheetah-like fashion.[11] However, in this scenario, the bear’s sheer physical mass would be a handicap. Arctodus skeletons do not articulate in a way that would have allowed for quick turns, an ability required of any predator that survives by killing agile prey.[10] Dr. Paul Matheus, paleontologist at the University of Alaska Fairbanks, determined that Arctodus' moved in a pacing motion like a camel, horse, and modern bears, making it built more for endurance than for great speed.[10] Arctodus simus, according to these arguments, was ill-equipped to be an active predator, leading some to conclude that it was a kleptoparasite,[10] using its enormous size to intimidate smaller predators such as dire wolves, Smilodon and American lions from their kills.
Recently, closer dietary research on the giant short-faced bear as well as the Cave Bear suggests that both bears were omnivores like most modern bears, and that the former did eat plants depending on availability.[12]
The giant short-faced bear became extinct about 12,000 years ago, perhaps partly because some of its large prey died out earlier, and partly also because of competition with the smaller, more omnivorous 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 pressure may also have contributed to its extinction, both directly (human hunting) or indirectly (due to the depletion of other large mammals which it may have followed to scavenge kills or depended upon as prey).
Arctodus simus, the giant short-faced bear, was featured in the ninth episode of Jurassic Fight Club, where it fought with an American Lion over a Steppe Bison kill made by the lion. The battle was based on a fossil find from the Natural Trap Cave, in the U.S. state of Wyoming. The program used the available fossil evidence to predict who would win in the aforementioned fight. In the end, the Arctodus won by throwing the 750-pound Mega-Lion into the enormous cave, where it died of the fall.