Biology:Megatheriidae

Short description: Extinct family of ground sloths

Megatheriidae Temporal range: Late Oligocene (Deseadan)-Early Holocene (Lujanian) ~29–0.008 Ma PreЄ Є O S D C P T J K Pg N
Eremotherium skeleton, NMNH, Washington, DC.
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Pilosa
Clade:	†Megatheria
Family:	†Megatheriidae J. E. Gray 1821
Type genus
†Megatherium americanum
Subgroups
†Thalassocnus? †Planopsinae †Planops †Prepoplanops †Prepotherium †Proprepotherium †Megatheriinae

Closeup of hand, showing claws

Closeup of skull

Megatheriidae is a family of extinct ground sloths that lived from approximately 23 mya—11,000 years ago.

Megatheriids appeared during the Late Oligocene (Deseadan in the SALMA classification), some 29 million years ago, in South America. The group includes the heavily built Megatherium (given its name 'great beast' by Georges Cuvier) and Eremotherium. An early genus that was originally considered a megatheriid, the more slightly built Hapalops, reached a length of about 1.2 metres (3.9 ft). The nothrotheres have recently been placed in their own family, Nothrotheriidae.

The skeletal structure of these ground sloths indicates that the animals were massive. Their thick bones and even thicker joints (especially those on the hind legs) gave their appendages tremendous power that, combined with their size and fearsome claws, provided a formidable defense against predators.

The earliest megatheriid in North America was Sibotherium which arrived 5.3 million years ago, after crossing the recently formed Panamanian land bridge. At more than five tons in weight, 6 metres (20 ft) in length, and able to reach as high as 5.2 metres (17 ft), Eremotherium was taller than an African bush elephant bull. Unlike relatives, this species retained a plesiomorphic 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 30 centimetres (1 ft) long.

Phylogeny

The following sloth family phylogenetic tree is based on collagen and mitochondrial DNA sequence data (see Fig. 4 of Presslee et al., 2019).

Folivora	Megalocnidae† (Caribbean sloths)         Scelidotheriidae†       Mylodontidae†     Choloepodidae (two-fingered sloths)               Megalonychidae   Megalonyx jeffersoni†   Bradypodidae   (three-fingered sloths)     B. torquatus       B. pygmaeus       B. tridactylus     B. variegatus               Nothrotheriidae   Nothrotheriops shastensis†         Megatheriidae   Megatherium americanum†

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

Folivora

Pseudoglyptodon     Bradypodidae  Bradypus   Eufolivora  Mylodontidae    Nematherium     Scelidotheriinae    Analcitherium       Neonematherium       Sibyllotherium       Proscelidodon       Catonyx       Scelidotherium     Valgipes                   Pseudoprepotherium     Orophodontinae?    Brievabradys       Octodontotherium       Paroctodontotherium       Octomylodon       Urumacotherium       Baraguatherium     Octodontobradys               Mylodontinae    Mylodon         Thinobadistes       Lestodon       Lestobradys     Bolivartherium               Simomylodon     Pleurolestodon         Glossotherium     Paramylodon                   Megatherioidea      Schismotherium     Pelecyodon       Megalonychidae    Hapalops       Hyperleptus       Eucholoeops       Pseudortotherium       Megalonychotherium     Megalonychinae    Pliometanastes       Megalonyx       Australonyx       Megistonyx     Ahytherium               Pliomorphus     Megalocninae    Megalocnus     Parocnus     Choloepodinae    Acratocnus       Neocnus     Choloepus                       Megatheria    Analcimorphus     Nothrotheriidae  Thalassocninae  Thalassocnus   Nothrotheriinae    Lakukullus         Mionothropus       Nothrotherium     Nothrotheriops           Pronothrotherium       Aymaratherium     Xyophorus             Megatheriidae  Planopsinae    Prepoplanops       Planops     Prepotherium       Megatheriinae      Diabolotherium     Megathericulus         Anisodontherium       Pyramiodontherium       Proeremotherium       Eremotherium     Megatherium

External links

• CTD: Megatheriidae
• Memidex: Megatheriidae

Wikidata ☰ Q784732 entry