''Nothrotheriops'' is an extinct genus of

ground sloth Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. They varied widely in size with the largest, belonging to genera '' Lestodon'', ''Eremotherium'' and ''Megatherium'', being around the size of elephants. ...

s endemic to

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

during the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

to early

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

(~2.5 Mya until 10,000 years ago). The genus contains two species, ''N. shastensis'' and ''N. texanus'', the former of which is also known as the Shasta ground sloth.

Taxonomy, history, and etymology

''Nothrotheriops'' fossils were first collected by the University of California's Anthropology Department during an exploration of caves at Potter Creek Cave in

Shasta County, California Shasta County (), officially the County of Shasta, is a County (United States), county located in the Northern California, northern portion of the U.S. state of California. Its population is 182,155 as of the 2020 census, up from 177,223 from t ...

, the fossils dating to the

late Quaternary The Holocene () is the current geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Qu ...

period.Sinclair, W. J. (1905). ''New mammalia from the Quaternary caves of California''. University of California Press.McDonald, H. G. (1995). ''Gravigrade xenarthrans'' from the early Pleistocene Leisey Shell Pit lA, Hillsborough County, Florida. ''Bulletin of the Florida Museum of Natural History'', ''37''(11), 245-373. These first fossils (

UCMP The University of California Museum of Paleontology (UCMP) is a paleontology museum located on the campus of the University of California, Berkeley. The museum is within the Valley Life Sciences Building (VLSB), designed by George W. Kelham a ...

8422), consisting of an incomplete mandibular ramus lacking teeth of an individual and 14 additional molars, were sent to the

University of California Museum of Paleontology The University of California Museum of Paleontology (UCMP) is a paleontology museum located on the campus of the University of California, Berkeley. The museum is within the Valley Life Sciences Building (VLSB), designed by George W. Kelham ...

, where they were described by paleontologist William Sinclair in 1904 as a new species of '' Nothrotherium, N. shastensis'' (species name meaning "from Shasta"). In 1916, Smithsonian paleontologist Oliver P. Hay named ''Nothrotherium texanus'' (species name meaning "from Texas") based on a partial skull that was transferred from

Baylor University Baylor University is a Private university, private Baptist research university in Waco, Texas, United States. It was chartered in 1845 by the last Congress of the Republic of Texas. Baylor is the oldest continuously operating university in Te ...

Waco, Texas Waco ( ) is a city in and the county seat of McLennan County, Texas, United States. It is situated along the Brazos River and Interstate 35, I-35, halfway between Dallas and Austin, Texas, Austin. The city had a U.S. census estimated 2024 popul ...

. The skull had been collected in the

strata of Wheeler County, Texas, and given to a clergyman, who then gave it to university staff in 1901. Many fossils were later referred to the two, but ''N. shastensis'' was not placed in a new genus until 1954, when it was placed in a new genus, ''Nothrotheriops'' ("near slothful beast", due to its similarity to ''Nothrotherium'') by Robert Hoffstetter during a study of fossil sloths. ''N. texanus'' was recombined into the genus in 1995, and had many fossils referred to it from Florida, the easternmost occurrence of the genus. Fossils of the best-known species, the Shasta ground sloth (''N. shastensis''), have been found throughout western North America, especially in the American Southwest. It is the ground sloth found in greatest abundance at the

La Brea Tar Pits La Brea Tar Pits comprise an active Paleontological site, paleontological research site in urban Los Angeles. Hancock Park was formed around a group of tar pits where natural Bitumen, asphalt (also called asphaltum, bitumen, or pitch; ''brea'' ...

. The most famous specimen was recovered from a

lava tube A lava tube, more rarely called a pyroduct, is a 'roofed conduit through which molten lava travels away from its vent'. If lava in the tube drains out, it will leave an empty cave. Lava tubes are common in low-viscosity volcanic systems. La ...

at Aden Crater in New Mexico, and was found to still have hair and tendon preserved.Lull, S. 1929
A remarkable ground sloth
. Memoirs of the Peabody Museum of Yale University, 3: 1-39. This nearly complete specimen is on display at the

Yale Yale University is a private Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the third-oldest institution of higher education in the United States, and one of the nine colonial colleges ch ...

Peabody Museum of Natural History The Peabody Museum of Natural History at Yale University (also known as the Yale Peabody Museum of Natural History or the Yale Peabody Museum) is one of the oldest, largest, and most prolific university natural history museums in the world. It ...

New Haven, Connecticut New Haven is a city of the U.S. state of Connecticut. It is located on New Haven Harbor on the northern shore of Long Island Sound. With a population of 135,081 as determined by the 2020 United States census, 2020 U.S. census, New Haven is List ...

. Numerous dung boli belonging to ''Nothrotheriops'' have also been found throughout the Southwestern United States and have provided an insight into the diet of these extinct animals. Nothrotheriops texanus Holotype USNM8353

Nothrotheriops texanus Holotype USNM8353

This genus's lineage dates back to the

Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...

. The ancestors of ''Nothrotheriops'' migrated to North America from South America as part of the

Great American Interchange The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which land ...

during the

Blancan The Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 4,750,000 to 1,806,000 years BP, a period of .PaleoBiology Database: ''Nothrotheriops'', basic info
/ref>

Description

Although ''N. shastensis'' was one of the smallest mainland

species, it still reached from snout to tail tip and weighed (one-quarter of a tonne) – much smaller than some of its contemporary species such as the ''

Eremotherium ''Eremotherium'' (from Greek for "steppe" or "desert" "beast": ἔρημος "steppe or desert" and θηρίον "beast") is an extinct genus of giant ground sloth in the family Megatheriidae. ''Eremotherium'' lived in southern North America, Cen ...

'', which could easily weigh over two tonnes and be long.Lange, Ian M., ''Ice Age Mammals of North America: A Guide to the Big, the Hairy, and the Bizarre'', Mountain Press Publishing Company, 2002. Pg. 83, 85 It had large, stout hind legs and a powerful, muscular tail that it used to form a supporting tripod whenever it shifted from a quadrupedal to a bipedal stance (i.e. ''Eremotherium'').Barton Miles & Co., Prehistoric America. A journey through the Ice Age and beyond. BBC publishing, 2002. Pg 108-9.

Paleobiology

''Nothrotheriops'' behaved like all typical ground sloths of North and South America, feeding on various plants, such as the desert globemallow,

cacti A cactus (: cacti, cactuses, or less commonly, cactus) is a member of the plant family Cactaceae (), a family of the order Caryophyllales comprising about 127 genera with some 1,750 known species. The word ''cactus'' derives, through Latin, ...

, and

yucca ''Yucca'' ( , YUCK-uh) is both the scientific name and common name for a genus native to North America from Panama to southern Canada. It contains 50 accepted species. In addition to yucca, they are also known as Adam's needle or Spanish-bayon ...

. It was hunted by various local predators, including dire wolves and ''

Smilodon ''Smilodon'' is an extinct genus of Felidae, felids. It is one of the best known saber-toothed predators and prehistoric mammals. Although commonly known as the saber-toothed tiger, it was not closely related to the tiger or other modern cats ...

'', from which the sloths may have defended themselves by standing upright on hind legs and tail, and swiping with their long fore claws, like their distant relative ''

Megatherium ''Megatherium'' ( ; from Greek () 'great' + () 'beast') is an extinct genus of ground sloths endemic to South America that lived from the Early Pliocene through the end of the Late Pleistocene. It is best known for the elephant-sized type spe ...

'', as conjectured in the BBC series '' Walking with Beasts''. The same claws could also have been used as tools to reach past the plant spines and grab softer flowers and fruits. Also, the Shasta ground sloth may have had a

prehensile Prehensility is the quality of an appendage or organ that has adapted for grasping or holding. The word is derived from the Latin term ''prehendere'', meaning "to grasp". The ability to grasp is likely derived from a number of different origin ...

tongue (like a

giraffe The giraffe is a large Fauna of Africa, African even-toed ungulate, hoofed mammal belonging to the genus ''Giraffa.'' It is the Largest mammals#Even-toed Ungulates (Artiodactyla), tallest living terrestrial animal and the largest ruminant on ...

) to strip leaves off branches. The Shasta ground sloth is believed to have played an important role in the dispersal of ''

Yucca brevifolia ''Yucca brevifolia'' (also known as the Joshua tree, yucca palm, tree yucca, and palm tree yucca) is a plant species belonging to the genus ''Yucca''. It is tree-like in habit, which is reflected in its common names. This monocotyledonous tree ...

'', or Joshua tree, seeds. Preserved dung belonging to the sloth has been found to contain Joshua tree leaves and seeds, confirming that they fed on the trees. The lack of Shasta ground sloths helping to disperse the seeds to more favourable climates may be causing the tree populations to suffer.

Distribution and habitat

A fossil find had been described from as far north as the Canadian province of

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

, but this report is believed to have been mistaken. The genus lived primarily in the southwestern region of the U.S., from the states of

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

and

Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

; it has also been found in

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

. The best-known historical specimen was found in a

at Aden Crater in

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

; it was found with hair and tendon still preserved. The Rampart Cave, located on the

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

side of the

Lake Mead National Recreation Area Lake Mead National Recreation Area is a U.S. national recreation area in Southeastern Nevada and Northwestern Arizona. Operated by the National Park Service, Lake Mead NRA follows the Colorado River corridor from the westernmost boundary of Gran ...

, has a plentiful amount of the sloth's hair and dung, both of which scientists used for

radiocarbon dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for Chronological dating, determining the age of an object containing organic material by using the properties of carbon-14, radiocarbon, a radioactive Isotop ...

to establish when it lived. The most recent credible dates from this and each of about half a dozen other southwestern caves are about 11,000 BP (13,000 cal BP). In addition to North America, fossils assigned to ''Nothrotheriops'' species have also been found as far south as

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

Santa Fe Province The Invincible Province of Santa Fe (, , lit. "Holy Faith") is a Provinces of Argentina, province of Argentina, located in the center-east of the country. Neighboring provinces are from the north clockwise Chaco Province, Chaco (divided by the 2 ...

. The youngest known bone of a single Shasta ground sloth (''N. shastensis'') individual from the

Devil Peak (Nevada) Devil Peak is a summit in the U.S. state of Nevada. The elevation is . The mountain's name comes from the Native Americans of the area, who named the summit "dwelling place of evil spirits". Variant names were "Big Devil", "Diablo Grande", "Looko ...

is dated to the early

, approximately 11,768-10787

calibrated In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known ...

years

Before Present Before Present (BP) or "years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because ...

, with dung remains from other localities also dated to the early Holocene.

References

External links

{{Taxonbar, from=Q1088778 Prehistoric sloths Pleistocene xenarthrans Pleistocene mammals of North America Prehistoric placental genera Fossil taxa described in 1954