Paramylodon

Paramylodon
Temporal range: late Pliocene to Pleistocene
Harlan's Ground Sloth (Paramylodon harlani)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Superorder: Xenarthra
Order: Pilosa
Family: †Mylodontidae
Subfamily: †Mylodontinae
Genus: †Paramylodon
Brown, 1903
Species: †P. harlani

Paramylodon is an extinct genus of ground sloth of the family Mylodontidae endemic to North America during the Pliocene through Pleistocene epochs, living from around ~4.9 Mya—11,000 years ago (approximately 4.889 million years).

Contents

Overview

Paramylodon is known from North America deposits as far south as Guatemala as well as Mexico and the United States and often mistaken as Glossotherium. Currently there is just one recognized species, P. harlani, that is commonly referred to as Harlan's ground sloth in honor of American paleontologist Dr. Richard Harlan who first discovered and described a lower jaw in 1835. Paramylodon exhibits the interesting characteristic of having had dermal ossicles, small bones embedded in the skin, presumably adding a degree of protection to the animal. This characteristic is also shared by the South American Mylodon.

Taxonomic History

The genus was created by Barnum Brown in 1903 with the species P. nebrascensis. The skull showed a number of characteristics similar to that of Mylodon harlani, which was also known from North America, but differed in the number of teeth present in the maxilla. Paramylodon had four teeth in the upper dentition, similar to that of Grypotherium darwini (=Mylodon darwini), but the then recognized genus of Mylodon possessed five upper teeth. P. nebrascensis was later considered to be a junior synonym of M. harlani by Stock (1925) given the large number of specimens from the La Brea Tar Pits that showed the presence of the upper caniniform to be variably lost in some specimens and retained in others. Thus the typical dental formula for the species of harlani is 5/4. Work by Kraglievich (1928) sorted through the long standing historical confusion concerning the taxonomic validity of Mylodon and Glossotherium, and determined what the type species of each genus was. An additional result was to recognize Paramylodon as generically different from Mylodon of South America and P. harlani was used as the species name as it had seniority over P. nebrascensis.

Until recently, Paramylodon was also viewed as a subspecies of Glossotherium and a number of institutions listed their specimens as Glossotherium harlani in part to work by Robertson (1976). Paramylodon is generically distinct from the South American genus of Glossotherium (see McAfee, 2007), although some question remains regarding the relationship of the late Blancan specimens that have been tentatively assigned as "Glossotherium" chapadmalense due to their seeming similarity to the South American species of the same name.

Fossil distribution

Sites and specimen ages (not complete):

Notable discoveries

Recently a Paramylodon harlani specimen was identified from the Tarkio Valley site in Iowa association with Megalonyx jeffersoni. This is the first occurrence of Paramylodon in Iowa, and probably the first time these species have been found in close association.[2] Since, these two species have been uncovered at the Fairmead Landfill Site and Irvington Site in California.

On December 3, 2009, the Press-Enterprise newspaper reports a specimen skull to have been recovered in San Timoteo Canyon (http://www.pe.com/localnews/inland/stories/PE_News_Local_S_sloth03.2dc60eb.html).

References

  1. ^ Paleobiology database: Medicine Hat Unit V collection.
  2. ^ "Fourth sloth discovered", comment on The Tarkio Valley Sloth Project, http://slothcentral.com/archives/529/comment-page-1#comment-1787

General References

External links