Plionarctos
| Plionarctos Temporal range:
| |
|---|---|
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Family: | Ursidae |
| Subfamily: | Tremarctinae |
| Genus: | †Plionarctos Frick, 1926 |
| Type species | |
| †Plionarctos edensis Frick, 1926
| |
| Species | |
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†P. edensis Frick, 1926 | |
Plionarctos is an extinct genus of short-faced bear endemic to North America from the Miocene to the Pliocene.
Taxonomy
[edit]Described by Childs Frick in 1926,[1] Plionarctos is the oldest known genus within the subfamily of the short-faced bears (Tremarctinae), and is believed to be ancestral to Arctodus, Arctotherium and Tremarctos.[2] A new species, P. harroldum, was described in 2001 from the White Bluffs Fauna in Washington from remains previously attributed to Ursus cf. abstrusus.[2] P. edensis is thought to be ancestral to P. harroldorum.[2]
Description
[edit]Plionarctos is thought to have weighed around the size of a smaller spectacled bear (60-150kg), and a skull length of 20cm.[3] Postcranial skeletons of Plionarctos are unknown.[3]
Diagnostics
[edit]Unlike other tremarctine bears, Plionarctos did not posses a premasseteric fossa. Although tooth sizes are similar, they also be differentiated from Tremarctos by the slightly shorter M2 molar.[3]
Paleobiology
[edit]Plionarctos existed between the middle Hemphillian faunal stage to the early Blancan faunal stage (7Mya - 2.9Mya).[3] Present on the coasts but rare in the Great Plains, Plionarctos is thought to have preferred more humid forested habitats.[3]
Like other tremarctine bears, Plionarctos is believed to have been sexually dimorphic.[3] A Plionarctos harroldum specimen from Taunton (Washington, 2.9Ma)[4] appears evolutionarily intermediate between P. harroldum and T. floridanus, such as being the size of T. floridanus.[5]
Fossil distribution
[edit]Sites and specimen ages - Middle Pleistocene remains from France were reported but have since been reassigned to Ursus.[6]
P. edensis
[edit]- Rattlesnake Formation, Grant County, Oregon (Plionarctos sp., Hemphillian, ca. 7Mya)[3]
- Montbrook Site, Levy County, Florida (Plionarctos sp., 5.5 - 5Mya)[7]
- Palmetto Mine, Polk County, Florida (Plionarctos sp., Upper Bone Valley Formation, 5 to 4.5Mya, Hemphillian)[3][8][9]
- Fort Green Mine, Polk County, Florida paleontological sites (Upper Bone Valley Formation, Hemphillian)[3]
- Ogalla Formation, Bear Tooth Slide, Brown County, Nebraska (Hemphillian)[3]
- Eden Formation, Riverside County, California (type P. edensis, Hemphillian)[3]
- Gray Fossil Site, Washington County, Tennessee (Plionarctos sp., ca. 4.9-4.5 Mya, Hemphillian)[10]
- Pipe Creek Sinkhole, Grant County, Indiana (5-4Mya, latest Hemphillian or earliest Blancan)[11]
- Aguanga Horizon, Riverside County, California (Blancan)[3]
P. harroldorum
[edit]- Bear Springs, Arizona (Early Blancan Red Knolls Fauna, ca. 3.1Mya)[12][13]
- White Bluffs fauna, Franklin County, Washington (Ringold Formation, type P. harroldorum)[2]
- Taunton site, Adams County, Washington (ca. 2.9Mya)[2][14]
References
[edit]- ^ Frick, Childs (1926). "The Hemicyoninæ and an American Tertiary Bear". Bulletin of the American Museum of Natural History. 56 (1): 111–119. hdl:2246/1321.
- ^ a b c d e Tedford, Richard H.; and Martin, James (2001-07-20). "Plionarctos, a tremarctine bear (Ursidae: Carnivora) from western North America". Journal of Vertebrate Paleontology. 21 (2): 311–321. doi:10.1671/0272-4634(2001)021[0311:PATBUC]2.0.CO;2. ISSN 0272-4634.
- ^ a b c d e f g h i j k l Janis, Christine M.; Scott, Kathleen M.; Jacobs, Louis L. (1998-05-28). Evolution of Tertiary Mammals of North America: Volume 1, Terrestrial Carnivores, Ungulates, and Ungulate Like Mammals. Cambridge University Press. ISBN 978-0-521-35519-3.
- ^ Morgan, James K.; Morgan, Neil H. (1995). "A New Species of Capromeryx (Mammalia: Artiodactyla) from the Taunton Local Fauna of Washington, and the Correlation with Other Blancan Faunas of Washington and Idaho". Journal of Vertebrate Paleontology. 15 (1): 160–170. Bibcode:1995JVPal..15..160M. doi:10.1080/02724634.1995.10011215. ISSN 0272-4634. JSTOR 4523614.
- ^ Tedford, Richard H.; and Martin, James (2001-07-20). "Plionarctos, a tremarctine bear (Ursidae: Carnivora) from western North America". Journal of Vertebrate Paleontology. 21 (2): 311–321. doi:10.1671/0272-4634(2001)021[0311:PATBUC]2.0.CO;2. ISSN 0272-4634.
- ^ Cregut-Bonnoure, Evelyne (15 August 1996). "A review of small Middle Pleistocene bears from France" (PDF). Acta Zoologica Cracoviensia. 39 (1): 89–101.
- ^ "About Montbrook". Montbrook Fossil Dig. Retrieved 2025-06-18.
- ^ Doughty, Evan M.; Wallace, Steven C.; Schubert, Blaine W.; Lyon, Lauren M. (2018). "First occurrence of the enigmatic peccaries Mylohyus elmorei and Prosthennops serus from the Appalachians: latest Hemphillian to Early Blancan of Gray Fossil Site, Tennessee". PeerJ. 6: e5926. doi:10.7717/peerj.5926. ISSN 2167-8359. PMC 6276594. PMID 30533292.
- ^ "Palmetto Fauna". Florida Vertebrate Fossils. Retrieved 2025-06-18.
- ^ Samuels, Joshua X.; Bredehoeft, Keila E.; Wallace, Steven C. (2018). "A new species of Gulo from the Early Pliocene Gray Fossil Site (Eastern United States); rethinking the evolution of wolverines". PeerJ. 6: e4648. doi:10.7717/peerj.4648. ISSN 2167-8359. PMC 5910791. PMID 29682423.
- ^ Farlow, James O.; Sunderman, Jack A.; Havens, Jonathan J.; Swinehart, Anthony L.; Holman, J. Alan; Richards, Ronald L.; Miller, Norton G.; Martin, Robert A.; Hunt, Robert M.; Storrs, Glenn W.; Curry, B. Brandon; Fluegeman, Richard H.; Dawson, Mary R.; Flint, Mary E.T. (2001). "The Pipe Creek Sinkhole Biota, a Diverse Late Tertiary Continental Fossil Assemblage from Grant County, Indiana". The American Midland Naturalist. 145 (2): 367–378. ISSN 0003-0031.
- ^ White Jr., Richard S.; Morgan, Gary S. (2005). "Arizonan Blancan Vertebrate Faunas in Regional Perspective". Vertebrate Paleontology of Arizona, Mesa Southwest Museum Bulletin. 11.
- ^ Morgan, Gary S.; White Jr., Richard S. (2005). "Miocene and Pliocene vertebrates from Arizona". Vertebrate Paleontology in Arizona. New Mexico Museum of Natural History and Science Bulletin. 29 – via ResearchGate.
- ^ Morgan, James K.; Morgan, Neil H. (1995). "A New Species of Capromeryx (Mammalia: Artiodactyla) from the Taunton Local Fauna of Washington, and the Correlation with Other Blancan Faunas of Washington and Idaho". Journal of Vertebrate Paleontology. 15 (1): 160–170. Bibcode:1995JVPal..15..160M. doi:10.1080/02724634.1995.10011215. ISSN 0272-4634. JSTOR 4523614.