Pliometanastes is an extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of giant ground sloths of the family Megalonychidae

Megalonychidae

Megalonychidae is a group of sloths including the extinct Megalonyx and the living two toed sloths. Megalonychids first appeared in the early Oligocene, about 35 million years ago, in southern Argentina , and spread as far as the Antilles by the early Miocene...

 endemic to North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 during the Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 epoch through very early Pliocene

Pliocene

The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

 epoch. Its fossils have been found across the southern U. S. from California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 to Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

.

Pliometanastes and Thinobadistes

Thinobadistes

Thinobadistes is an extinct genus of actively mobile ground sloth of the family Mylodontidae, endemic to North America during the Miocene-Pleistocene epochs. It lived from 13.6—5.3 mya, existing for approximately ....

were the first of the giant sloths to appear in N. America. Both were in N. America before the Panamanian Land Bridge

Isthmus of Panama

The Isthmus of Panama, also historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country of Panama and the Panama Canal...

 formed around 2.5 million years ago. It is then reasonable to presume that the ancestors of Pliometanastes island-hopped across the Central American Seaway

Central American Seaway

The Central American Seaway, also called the Panamanic Seaway or Inter-American Seaway was an ancient body of water that once separated North America from South America...

 from South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

, where ground sloths arose.

Pliometanastes gave rise to Megalonyx

Megalonyx

Megalonyx is an extinct genus of giant ground sloths of the family Megalonychidae endemic to North America from the Hemphillian of the Late Miocene through to the Rancholabrean of the Pleistocene, living from ~10.3 Mya—11,000 years ago, existing for approximately .-Taxonomy:The generic name...

. Their closest extant relatives are the two-toed arboreal sloths (Choloepus).

Taxonomy

Pliometanastes was named by Hirschfeld and Webb (1968). Its type is Pliometanastes protistus. It was assigned to Megalonychidae by Hirschfeld and Webb (1968) and Carroll (1988).

Fossil distribution

Sites and ages of specimens (not complete list):

• Withlacoochee River Site 4A, Marion County, Florida
  Marion County, Florida
  Marion County is a county located in the U.S. state of Florida. The U.S. Census Bureau 2006 estimate for the county is 316,183. Its county seat is Ocala....
  
   ~10.3-4.9 Mya.
• Haile Site V/XIXA
  Haile Quarry site
  The Haile Quarry or Haile sites are an Early Miocene and Pleistocene assemblage of vertebrate fossils located in the Haile quarries, Alachua County, northern Florida. The assemblage was discovered during phosphate mining, which began in the late 1940s. Haile sites are found in the Alachua Formation...
  
  , Alachua County, Florida
  Alachua County, Florida
  Alachua County is a county located in the U.S. state of Florida. The U.S. Census Bureau 2006 estimate for the county is 227,120. Its county seat is Gainesville, Florida. Alachua County is the home of the University of Florida and is also known for its diverse culture, local music, and artisans...
  
   ~10.3-4.9 Mya.
• Box T, Lipscomb County, Texas ~23-5.3 Mya.
• Klipstein Ranch site 3, Kern County, California
  Kern County, California
  Spreading across the southern end of the California Central Valley, Kern County is the fifth-largest county by population in California. Its economy is heavily linked to agriculture and to petroleum extraction, and there is a strong aviation and space presence. Politically, it has generally...
  
  ~23-5.3 Mya.