Plionarctos is an extinct genus of bear endemic to North America from the Miocene to the Pliocene, ~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. Plionarctos 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), and is believed to be ancestral to the clade.
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