Megatheriidae is a family of

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

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 that lived from approximately 23 mya—11,000 years ago. Megatheriids appeared during the

Late Oligocene The Chattian is, in the geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...

(

Deseadan The Deseadan () age is a period of geologic time (29.0–21.0 Ma) within the Oligocene epoch of the Paleogene to the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification of South America. It follows the Tingu ...

in the SALMA classification), some 29 million years ago, in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. The group includes the largest known ground sloths, the elephant sized ''

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 ...

'' (given its name 'great beast' by

Georges Cuvier Jean Léopold Nicolas Frédéric, baron Cuvier (23 August 1769 – 13 May 1832), known as Georges Cuvier (; ), was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...

) and ''

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 ...

''. An early genus that was originally considered a megatheriid, the more slightly built ''

Hapalops ''Hapalops'' is an extinct genus of ground sloth from the Early to Late Miocene of Brazil (Solimões Formation), Bolivia ( Honda Group), Colombia ( Honda Group),Croft, 2007, p.300 and Argentina (Santa Cruz Formation) in South America.

'', reached a length of about . The nothrotheres have recently been placed in their own family,

Nothrotheriidae Nothrotheriidae is a family of extinct ground sloths that lived from approximately 17.5 mya—10,000 years ago, existing for approximately . Previously placed within the tribe Nothrotheriini or subfamily Nothrotheriinae within Megatheriidae, they ...

. The skeletal structure of these ground sloths indicates that the animals were massive. Their thick

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

s and even thicker

joint A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

s (especially those on the hind legs) gave their appendages tremendous power that, combined with their size and fearsome

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or Arthro ...

s, provided a formidable defense against predators. The earliest megatheriid in

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 ...

was ''

Sibotherium ''Sibotherium'' is an extinct genus of ground sloth in the family Megatheriidae that lived in what is now Costa Rica during the Late Miocene. It was a large ground sloth, weighing more than 2,500 kg. Discovery Fossils of ''Sibotherium'' ...

'' which arrived 5.3 million years ago, after crossing the recently formed

Panama Panama, officially the Republic of Panama, is a country in Latin America at the southern end of Central America, bordering South America. It is bordered by Costa Rica to the west, Colombia to the southeast, the Caribbean Sea to the north, and ...

nian land bridge. At more than five tons in weight, in length, and able to reach as high as , ''

'' when fully erect was taller than an

African bush elephant The African bush elephant (''Loxodonta africana''), also known as the African savanna elephant, is a species of elephant native to sub-Saharan Africa. It is one of three extant elephant species and, along with the African forest elephant, one ...

bull. Unlike relatives, this species retained a

plesiomorph In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral Phenotypic trait, character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorph ...

ic extra claw. While other species of ''Eremotherium'' had four fingers with only two or three claws, ''E. eomigrans'' had five fingers, four of them with claws up to nearly long.De Iuliis and Cartelle (1999)

Phylogeny

The following phylogeny is based on Varela ''et al''. 2019.

References

External links

*
CTD: Megatheriidae

Memidex: Megatheriidae
{{Taxonbar, from=Q784732 Prehistoric mammal families Burdigalian first appearances Holocene extinctions Neogene mammals of South America Neogene mammals of North America Pleistocene mammals of South America Pleistocene mammals of North America Taxa named by John Edward Gray