Plionarctos

Plionarctos is an extinct genus of mammals of the family Ursidae (bears) endemic to North America and Europe during Miocene through Pleistocene, living from ~10.3—3.3 Mya, existing for about 7 million years.

Indarctos (10.7—9.2 Mya) preceded Plionarctos by only a few thousand years and was a contemporary of that bear and shared its habitat. Plionarctus preceded and was also contemporary with Tremarctos floridanus (4.9 million — 11,000 years ago) and shared its habitat.

Plionarctos is the oldest known genus within the subfamily of the short-faced bears (Tremarctinae) endemic to the Americas, and is believed to be ancestral to the clade.

Taxonomy

Plionarctos was named by Frick (1926). Its type is Plionarctos edensis. It was assigned to Ursidae by Frick (1926) and Carroll (1988); and to Tremarctini by Hunt (1998).^[1][2]

Morphology

Body mass

Two specimens were examined by Legendre and Roth for body mass.^[3]

• Specimen 1 was estimated to weigh 165.5 kg (360 lb).
• Specimen 2 was estimated to weigh 25.3 kg (56 lb).

Fossil distribution

Sites and specimen ages:

• Ile de Ratonneau Breccia, Provence, France about ~800,000—100,000 years ago
• Fort Green Mine, Polk County, Florida paleontological sites about 10.3—4.9 Mya
• Taunton site, Adams County, Washington (P. harroldorum) about 4.9—1.8 Mya (Plionarctos harroldorum)
• Pipe Creek Sinkhole, Grant County, Indiana (P. edensis) about 10.3—1.8 Mya
• Palmetto Mine, Polk County, Florida 7.9—7.8 Mya
• Gray Fossil Site, Washington County, Tennessee about 7.0-4.5 Mya

References