''Thinobadistes'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

ground sloth Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. The term is used to refer to all extinct sloths because of the large size of the earliest forms discovered, compared to existing tree sloths. The Caribb ...

of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Mylodontidae endemic to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

during the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Hemphillian). It lived from 10.3 to 4.9 mya, existing for approximately . ''Thinobadistes'' and '' Pliometanastes'' were the first of the giant sloths to appear in N. America. Both ''Pliometanastes'' and ''Thinobadistes'' were in N. America before the Panamanian Land Bridge formed around 2.5 million years ago. It is then reasonable to presume that the ancestors of ''Thinobadistes'' island-hopped across the

Central American Seaway The Central American Seaway (also known as the Panamanic Seaway, Inter-American Seaway and Proto-Caribbean Seaway) was a body of water that once separated North America from South America. It formed during the Jurassic (200–154 Ma) during the br ...

from

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...

, where sloths in general first evolved.

Description

Two specimens of ''Thinobadistes'' have been estimated to weigh 948 kg and 1066 kg each.

History and taxonomy

The first reported discovery of ''Thinobadistes'' fossils came in 1887 when in Pleistocene deposits in

Levy County Levy County is a county located on the Gulf coast and in the northern part of the U.S. state of Florida. As of the 2020 census, the population was 42,915. Its county seat is Bronson. History Levy County was created in 1845, after the Semino ...

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and ...

, a member of the

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

, possibly famous collector

John Bell Hatcher John Bell Hatcher (October 11, 1861 – July 3, 1904) was an American paleontologist and fossil hunter known as the "king of collectors" and best known for discovering ''Torosaurus'' and ''Triceratops'', two genera of dinosaurs described by O ...

, collected an astragalus of a large mylodontid, though the fossil was referred to '' Mylodon harlani'' until 1919.Hay, O. P. (1919). Descriptions of some mammalian and fish remains from Florida of probably Pleistocene age. The fossil was made as the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

(

USNM The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with ...

3335) of ''Thinobadistes segnis'' by Oliver P. Hay in 1919, who believed it was a close relative of '' Gnathopsis''.Webb, S. D. (1989). Osteology and relationships of Thinobadistes segnis, the first mylodont sloth in North America. ''Advances in neotropical mammalogy'', ''1989'', 469-532. ''Thinobadistes'' ''segnis''' holotype was likely collected at "Mixon's Bone Bed", which was the site at which many more ''T. segnis'' fossils were found during the late 1930s and early 1940s by Frick Laboratory. These fossils gave a comprehensive view on the taxon, including fossils from the skull and teeth. It wasn't until 1989 that many of the fossils were fully described by S. D. Webb, who also described many more ''Thinobadistes'' fossils from areas like the

Texas Panhandle The Texas Panhandle is a region of the U.S. state of Texas consisting of the northernmost 26 counties in the state. The panhandle is a square-shaped area bordered by New Mexico to the west and Oklahoma to the north and east. It is adjacent to ...

and Withlacoochee River.Hulbert, R. C., Poyer, A. R., & Webb, S. D. (2002). Tyner Farm, a new early Hemphillian local fauna from north-central Florida. ''Journal of Vertebrate Paleontology'', ''22''(3). Some of the younger and larger fossils were put into a new species, ''Thinobadistes wetzeli'', which was also based on an astragalus found in Hemphillian deposits of the Withlacoochee River, Florida.

Fossil distribution

Fossils of ''Thinobadistes segnis'' have only been found at 2 sites, both early Hemphillian, the type quarry at "Mixon's Bone Bed" in

Levy County, Florida Levy County is a county located on the Gulf coast and in the northern part of the U.S. state of Florida. As of the 2020 census, the population was 42,915. Its county seat is Bronson. History Levy County was created in 1845, after the Semi ...

and a single partial molar found was at McGehee Farm in western Alachua County, Florida. The second named species, ''T. wetzeli'', is from the lower early Hemphillian and has a wider distribution, with 2 sites containing fossils near the Withlacoochee River, Florida, 1 at Tyner Farm also in Alachua County, and material of a juvenile found in the

. Fossils from an unknown species were found in the youngest ''Thinobadistes-''bearing deposits at Coffee Ranch in the Texas Panhandle.Dalquest, W. W. (1983). ''Mammals of the Coffee Ranch Local Fauna Hemphilian of Texas''. Texas Memorial Museum, The University of Texas at Austin.

References

Prehistoric sloths Pliocene xenarthrans Miocene xenarthrans Zanclean extinctions Miocene mammals of North America Pliocene mammals of North America Hemphillian Fossil taxa described in 1919 {{paleo-mammal-stub