Bradypodidae

Three-toed sloths
Brown-throated three-toed sloth (Bradypus variegatus)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Pilosa
Suborder:	Folivora
Family:	Bradypodidae
Genus:	Bradypus Linnaeus, 1758
Type species
Bradypus tridactylus Linnaeus, 1758
Species
4, see text
Green: B. variegatus, Blue: B. tridactylus, Red: B. torquatus

4, see text

The three-toed sloths are tree-living mammals from South and Central America. They are the only members of the genus Bradypus and the family Bradypodidae. The four living species of three-toed sloths are the brown-throated sloth, the maned sloth, the pale-throated sloth, and the pygmy three-toed sloth.

A study of and 16S rRNA sequences suggests that B. torquatus diverged from B. variegatus and B. tridactylus about 12 million years ago, while the latter two split 5 to 6 million years ago. The diversification of B. variegatus lineages was estimated to have started 4 to 5 million years ago.

Although similar to the somewhat larger and generally faster-moving two-toed sloths, the two genera are placed in different families. Recent phylogenetic analyses support the morphological data from the 1970s and 1980s that the two genera are not closely related and that each adopted their arboreal lifestyles independently. It is unclear from which ground-dwelling sloth taxa the three-toed sloths evolved or whether they retain their arboreality from the last common ancestor of sloths; the two-toed sloths appear to nest phylogenetically within one of the divisions of ground-dwelling Caribbean megalonychids, thus probably either descended from them or are part of a clade that invaded the Caribbean multiple times. Both types of sloth tend to occupy the same forests; in most areas, a particular species of three-toed sloth and a single species of the larger two-toed type will jointly predominate. Famously slow-moving, the sloth travels at an average speed of 0.24 km/h (0.15 mph).

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