Nothrotheriidae is a family of

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

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 Caribbe ...

s that lived from approximately 17.5

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—10,000 years ago, existing for approximately .PaleoBiology Database: Nothrotheriidae, basic info
/ref> Previously placed within the tribe Nothrotheriini or subfamily Nothrotheriinae within Megatheriidae, they are now usually placed in their own family, Nothrotheriidae. Nothrotheriids appeared in the

Burdigalian The Burdigalian is, in the geologic timescale, an age (geology), age or stage (stratigraphy), stage in the early Miocene. It spans the time between 20.43 ± 0.05 annum, Ma and 15.97 ± 0.05 Ma (million years ago). Preceded by the Aquitanian (sta ...

, some 19.8 million years ago, in South America. The group includes the comparatively slightly built ''

Nothrotheriops ''Nothrotheriops'' is a genus of Pleistocene ground sloth found in North America, from what is now central Mexico to the southern United States. This genus of bear-sized xenarthran was related to the much larger, and far more famous ''Megatherium ...

'', which reached a length of about . While nothrotheriids were small compared to some of their megatheriid relatives, their claws provided an effective defense against predators, like those of larger

anteater Anteater is a common name for the four extant mammal species of the suborder Vermilingua (meaning "worm tongue") commonly known for eating ants and termites. The individual species have other names in English and other languages. Together with ...

s today.

Evolution

During the late

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 ...

and

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Thalassocnus'' of the west coast of South America became adapted to a shallow-water marine lifestyle. However, the family placement of ''Thalassocnus'' has been disputed; while long considered a nothrotheriid, one recent analysis moves it to Megatheriidae, while another retains it in a basal position within Nothrotheriidae. The only known nothrotheriid in North America was ''Nothrotheriops'', which appeared at the beginning of the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

, about 2.6 Ma ago.PaleoBiology Database: ''Nothrotheriops'', basic info
/ref> '' Nothrotherium'' reached Mexico ( Nuevo Leon) by the late Pleistocene.PaleoBiology Database: ''Nothrotherium'', basic info
/ref> Rampart Cave interior sloth dung

The last ground sloths in North America belonging to ''Nothrotheriidae'', the Shasta ground sloth (''Nothrotheriops shastensis''), died so recently that their dried

subfossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

ized dung has remained undisturbed in some cavessuch as the Rampart Cave, located on the

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

side of the Lake Mead National Recreation Area as if it were just recently deposited. A Shasta ground sloth skeleton, found in a

lava tube A lava tube, or pyroduct, is a natural conduit formed by flowing lava from a volcanic vent that moves beneath the hardened surface of a lava flow. If lava in the tube empties, it will leave a cave. Formation A lava tube is a type of lava ca ...

Aden Crater Aden Crater is a small shield volcano located in Doña Ana County, about southwest of Las Cruces, New Mexico. It is located in the northwest part of the Aden-Afton basalt field, which is part of the central area of the Potrillo volcanic field ...

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

, still had skin and hair preserved, and is now at the Yale Peabody Museum. The largest samples of ''Nothrotheriops'' dung can be found in the collections of the

National Museum of Natural History 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 7 ...

Phylogeny

The following sloth family phylogenetic tree is based on collagen and mitochondrial DNA sequence data (see Fig. 4 of Presslee ''et al''., 2019). Here is a more detailed phylogeny of the Nothrotheriidae based on Varela ''et al''. 2018.

References

External links

{{Taxonbar, from=Q16879160 Prehistoric mammal families Burdigalian first appearances Holocene extinctions Neogene mammals of South America Quaternary mammals of South America Quaternary mammals of North America Taxa named by Florentino Ameghino