Careful study of fossil bone or tooth anatomy yields much exact information about placement and strength of muscles, tendons, ligaments, nerves, and blood vessels. In rare cases, skin and hair impressions or actual skin or hair is preserved. Body weight is more difficult to gauge because fat leaves no impression on the skeleton.
|Estimated Body Weight*||1019 kg (2,246 lbs) for Actodus simus|
|Estimated Height at Shoulder||1.6-1.7 m (5.25-5.6 ft)|
|Estimated Standing Upright Height||3 m (9.8 ft)|
* For comparison, an average male polar bear's weight is about 600 kg (1323 lb) and may be up to 800 kg (1,764 lb); a Brown Bear's weight varies with diet but is generally less than that of a Polar Bear.
Note: Estimates in literature vary widely for Arctodus; this is a highly dimorphic species, as are living bears, with extreme differences between males and females; many estimates based on very small sample sizes
Arctodus simus is an enormous extinct bear with a domed skull, wide snout, a short back, with tooth and jaw features that suggest omnivorous habits. (Figueirido et al 2010)
Arctodus simus was the largest Pleistocene carnivore on land.
A. pristinus was much smaller, with a similar proportions.
Distinct sexual dimorphism; males are about 15% larger than females.
The living tremarctine bear, Tremarctos, has 53 chromosomes; all other bears have 74.
Bones are quite light for their size.
Toes align forward, rather than inward as in other bears.
Feet are plantigrade (walked flat-footed)
Fingers have a small bone in the wrist, the radial sesamoid, which is enlarged, forming a "false thumb" somewhat similar to that of the giant panda and the spectacled bear (Salesa et al 2006)
The articulation of the lower and upper jaws falls above the tooth row, as in plant-eating hoofed mammals. (Sorkin 2006)
Eye sockets are small and directed somewhat to the side, similar to those of plant-eating hoofed mammals. (Sorkin 2006)
Figueirido et al (2009)
Figueirido et al (2010)
Kurtén & Anderson (1980)
Salesa et al (2006)