Short-Faced Bear, Arctodus
July 2009

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*How Do We Know This? Like living animals, fossil remains of once-living animals are
classified and grouped according to their relationships to each other and to their ancestors.

(Agnarsson et al 2010) (Figueirido et al 2010) (Hunt 1997) (Kurtén 1968) (Kurtén & Anderson 1980) (McKenna and Bell 1997) (Tedford & Martin 2001) (Wayne et al 1989) (Li et al 2007)

Describer (Date): E. D. Cope 1879 for Arctodus simus

Kingdom: Animalia
    Phylum: Chordata
        Class: Mammalia
             Order: Carnivora
                    Family: Ursidae (bears)
                          Subfamily: Tremarctinae (the "running bears")
                                    Genus: Arctodus
                                          Species: Arctodus simus (extinct) short-faced bear
                                          Species: Arctodus pristinus (extinct) lesser short-faced bear
                                    Genus: Tremarctos
                                          Species: Tremarctos ornatus - spectacled bear
                          Subfamily: Ursinae (brown, American black, Asiatic black, sloth, sun, polar bears
                                       and many extinct bear species)
                          Subfamily: Ailuropodinae (includes giant pandas)     

Taxonomic History and Nomenclature Phylogeny

*How Do We Know This? Scientists use knowledge of the earth's rocks, global plate
movements, and the chemical process of fossilization to make sense of fossil
distribution patterns and ancient habitats.

(Gillette & Madsen 1992, 1993) (Kurtén 1967)(Kurtén & Anderson 1980)(Scott & Cox 1993)

Prehistoric Distribution:

*How Do We Know This? 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.

(Christiansen 1999) (Figueirido et al 2009) (Figueirido et al 2010) (Garshelis 2009)(Kurtén & Anderson 1980) (Salesa et al 2006) (Sorkin 2006)

Estimated Body Weight: 1019 kg (2,246 lbs) for A. simus. 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
Estimated Height at Shoulder: 1.6-1.7 m (5.25-5.6 ft); 3 m (9.8 ft) estimated standing upright height
Tail Length: vestigial

General Description Teeth   Pelage   Sexual Dimorphism Other Physical Characteristics

*How Do We Know This? Since direct observation of a fossil animal's behavior isn't
possible, paleontologists use comparison and contrast with living animals for guidance.
Tracks can sometimes reveal further clues.

(Barnes et al 2002) (Figueirido et al 2009) (Figueirido et al 2010)(Richards et al 2008)

Social Life
Interspecies Interaction

*How Do We Know This? Clues to fossil mammals' diets come from teeth,skull shape,
from fossil dung and gut contents, from lab analysis of isotopes in bone and teeth,
and by looking at diets of similar modern animals.

(Barnes et al 2002) (Bocherens et al 2006) (Figueirido et al 2009) (Kurtén 1988)(Matheus 1995) (Matheus et al 2002) (Richards et al 2008)(Ruxton & Houston 2004)(Sorkin 2006)

*How do We Know This? Isotope studies of elements present fossil bones and tusks
in microscopic quantities give information about timing of reproductive stress, and timing
of nursing. Clues to stages of development come from tooth replacement patterns
and closure of sutures in skull and limb bones.

(Matheus 1995) (Schubert and Kaufmann 2003)

Life Stages

*How do We Know This? Abnormalities in fossil bones may show evidence
of arthritis, cancer, nutritional stress, fractures and more.

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