Arctodus

genus of mammals

Arctodus is an extinct genus of short-faced bear endemic to North America during the Pleistocene era about 2.5 million years ago to 12,800 years ago. There were two species, Arctodus pristinus and Arctodus simus.

Arctodus
Temporal range: Pleistocene 2.5–0.0128 Ma
A. simus from the La Brea tar pits
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Ursidae
Subfamily: Tremarctinae
Genus: Arctodus
Leidy, 1854
Type species
Arctodus pristinus
Leidy, 1854
Species
  • A. pristinus (Leidy, 1854)
  • A. simus (Cope, 1879)
Maximum range of Arctodus simus.

The giant short-faced bear, Arctodus simus, evolved from Arctodus pristinus during the middle Pleistocene of North America, around 1.3 million years ago. Both species were omnivorous, feeding on tall vegetation and large mammals. Arctodus simus might have been the largest predatory land mammal that ever lived in North America.

Habitat

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Both species of Arctodus lived in different habitats, with Arctodus pristinus preferred dense forests in eastern North America,[1] and Arctodus simus inhabiting open forests in western North America. However, after the extinction of Arctodus pristinus, the giant short-faced bear spread east in small numbers.[2]

Arctodus pristinus was particularly common on the east coast, with the largest concentrations being in Florida.[3] Additional finds are from Pennsylvania, West Virginia, Kansas and Aguascalientes (Mexico).[4][5]

Arctodus simus lived in much of North America, ranging from Alaska to Puebla in the west,[6] to Virginia and Florida in the east.[2][5] This species is first found in California,[5][7] and was most common in the savannas and pinon-juniper woodlands of the western United States and Mexico, where many other megafauna lived.[8][9]

Fossils

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The oldest Arctodus fossils are from the Kissimmee River & Santa Fe River paleontological sites in Florida, belonging to Arctodus pristinus.[3] The first fossils of the Arctodus simus were found the Potter Creek Cave in Shasta County, California, by Edward Drinker Cope,[10] with the oldest being from Irvington, California.[5]

Paleontologists have found only one Arctodus simus skeleton in Indiana.[11] It is famous because it was the biggest most-nearly complete skeleton of a giant short-faced bear ever found in America. The original bones are in Chicago's Field Museum of Natural History.[12]

Males were much larger than females.[13] When it was standing on its back legs, Arctodus simus was 8–11 feet (2.4–3.4 m) tall.[14] A 2010 study estimated the weight of six Arctodus simus individuals, with a weight range between 317 kg (699 lb) and 957 kg (2,110 lb). In comparison, Arctodus pristinus specimens have been calculated to an average of ~133 kg (293 lb),[15] although some northern and western Arctodus pristinus were the same size as small Arctodus simus.[5]

Behavior

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Both species were omnivores, browsing on shrubs and trees, and eating browsers like deer, camels, llamas, tapirs, ground sloths, and wood bison,[16][17] Dental damage from eating carbohydrates,[18][19][20] and seeds in Arctodus simus' poop proves plants were consumed,[21][22] while bone damage on prey matches both Arctodus species' teeth.[13][23][24][25] Analyses of Arctodus simus' bone chemicals confirm that the giant short-faced bear lived in open forests and other vegetated areas, and sometimes ate other open forest inhabitants.[17][26][27][28][29][30]

 
The skeleton of Arctodus pristinus, from The Bishop Museum of Science and Nature, Florida.

Past research

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One theory was that the giant short-faced bear was an active predator, attacking herbivores directly.[31] Another theory was that it let faster predators make the kill, then bullied them off the carcass, being a scavenger.[32] Finally, anatomy led some to believe it was a herbivore.[33] Modern research establishes all three behaviors were present in Arctodus simus.[16]

Previous theories also suggested that brown bears caused the extinction of Arctodus simus, and that the giant short-faced bear prevented people from migrating into North America.[34] However, these ideas have been rejected,[35] with new dates confirming both co-existed with Arctodus simus.[36][37]

Extinction

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The replacement of hot & humid forests with open habitats, along with competition with black bears and Tremarctos floridanus, led to the extinction of Arctodus pristinus 300,000 years ago.[3] Arctodus simus went extinct around 12,800 years ago,[38][39] which was likely due to ecological collapse leading to fewer prey and quality vegetation.[34]

References

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  1. Russell, Dale A.; Rich, Fredrick J.; Schneider, Vincent; Lynch‐Stieglitz, Jean (May 2009). "A warm thermal enclave in the Late Pleistocene of the South‐eastern United States". Biological Reviews. 84 (2): 173–202. doi:10.1111/j.1469-185X.2008.00069.x. ISSN 1464-7931.
  2. 2.0 2.1 Schubert, Blaine W.; Hulbert, Richard C.; Macfadden, Bruce J.; Searle, Michael; Searle, Seina (January 2010). "Giant short-faced bears ( Arctodus simus ) in Pleistocene Florida USA, a substantial range extension". Journal of Paleontology. 84 (1): 79–87. doi:10.1666/09-113.1. ISSN 0022-3360.
  3. 3.0 3.1 3.2 Emslie, Steven D. (1995). "The fossil record of Arctodus pristinus (Ursidae: Tremarctinae) in Florida" (PDF). Bulletin of the Florida Museum of Natural History. 37: 501–514 – via Florida Museum.
  4. I. Ferrusquia-Villafranca. 1978. Bol Univ Nac Aut Mex Inst Geol 101:193-321
  5. 5.0 5.1 5.2 5.3 5.4 Richards, Ronald L.; Churcher, C.S.; Turnbull, William D. (1996-12-31), "Distribution and size variation in North American Short-faced bears, Arctodus simus", Palaeoecology and Palaeoenvironments of Late Cenozoic Mammals, University of Toronto Press, pp. 191–246, doi:10.3138/9781487574154-012, ISBN 978-1-4875-7415-4, retrieved 2023-11-30
  6. C.S. Churcher, A.V. Morgan, and L.D. Carter. 1993. Arctodus simus from the Alaskan Arctic Slope. Canadian Journal of Earth Sciences 30(5):1007-1013, collected by A.V. Morgan
  7. M.L. Cassiliano. 1999. Biostratigraphy of Blancan and Irvingtonian mammals in the Fish Creek-Vallecito Creek section, southern California, and a review of the Blancan-Irvingtonian boundary. Journal of Vertebrate Paleontology 19(1):169-186
  8. Pichardo, Mario (2003-06-13). "Overview of Central Mexican Prehistory: Morphostratigraphy, Chronostratigraphy, Biostratigraphy". Anthropologischer Anzeiger. 61 (2): 141–174. doi:10.1127/anthranz/61/2003/141. ISSN 0003-5548.
  9. Martin, Larry; Neuner, A. (1978-01-01). "The End of the Pleistocene in North America". Transactions of the Nebraska Academy of Sciences and Affiliated Societies.
  10. Cope E.D. 1879. The cave bear of California. American Naturalist, 13:791.
  11. Richards, Ronald L.; Richards, Ronald L.; Neiburger, Ellis J.; Turnbull, William D. (1995). Giant short-faced bear (Arctodus simus yukonensis) remains from Fulton County, northern Indiana. Chicago, Ill: Field Museum of Natural History.
  12. Stark, Mike (April 2022). Chasing the Ghost Bear: On the Trail of America's Lost Super Beast. U of Nebraska Press. ISBN 978-1-4962-2902-1.
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