Arctodus pristinus

Arctodus pristinus is an extinct species of short-faced bear belonging to the genus Arctodus , which lived in North America during the Pleistocene, approximately between 2.5 million and 10,000 years ago. It was a close relative of Arctodus simus , although smaller in size and with some morphological differences in its skeleton that suggest different ecological adaptations. Its fossil remains have been found mainly in the southeastern United States, from Florida to Texas, indicating that it inhabited more temperate and forested regions compared to its giant relative, which was distributed in more open habitats in the north.

The skeleton of Arctodus pristinus reveals a large and powerful animal, although more graceful than modern bears. It is estimated to have stood up to 1.5 metres tall at the withers when on all fours and could have reached 2.7 metres tall when standing on its hind legs. Its weight ranged from 300 to 600 kg , being noticeably lighter than Arctodus simus , which could weigh over a ton. Its skull was elongated and had a morphology characteristic of short-faced bears, with a reduced snout compared to other ursids, possibly giving it a more powerful bite.

The limbs of Arctodus pristinus were long and slender in proportion to its body, a distinctive trait of tremarctines, the group of bears to which it belonged. Its bone structure suggests that it was a relatively agile runner for its size, although not as adapted to running as Arctodus simus . The metacarpals and metatarsals were long, giving it a wide stride, but its overall postcranial structure indicates that it probably relied more on strength and endurance than extreme speed.

Its forelimbs were robust, with large, curved claws that would have been useful for both predation and object manipulation or digging. Its teeth show a combination of omnivore characteristics with both scavenging and predatory tendencies. Although it had large molars capable of crushing plant matter, its incisors and canines were sharp and well developed, suggesting that it may have been an opportunistic predator, combining hunting with scavenging of large Pleistocene mammals.

Unlike Arctodus simus , which is thought to have been better adapted to life on open plains, Arctodus pristinus probably inhabited more forested and humid regions, where its diet and behaviour would have been more varied. Some studies have suggested that it may have competed with other large carnivores of its time, such as Smilodon and dire wolves ( Canis dirus ), although its exact role in the Pleistocene food chain remains a matter of debate.

The extinction of Arctodus pristinus occurred towards the end of the Pleistocene, coinciding with the disappearance of many North American megafauna species. Factors such as climate change and the pressure exerted by the arrival of the first humans in America are thought to have contributed to its disappearance. Its study continues to provide key information on the evolution of bears and the ecological dynamics of Pleistocene ecosystems.

Approximate measurements of Arctodus:

• Scale 1:35
• Length 61 mm
• Height 46 mm
• Width 24 mm

• Scale 1:20
• Length 107 mm
• Height 80 mm
• Width 41 mm