The three-toed or three-fingered sloths are arboreal neotropical mammals. They are the only members of the genus Bradypus (meaning "slow-footed" in Ancient Greek) and the family Bradypodidae. The five living species of three-toed sloths are the brown-throated sloth, the maned sloth, the pale-throated sloth, the southern maned sloth, and the pygmy three-toed sloth. In complete contrast to past morphological studies, which tended to place Bradypus as the sister group to all other folivorans, molecular studies place them nested within the sloth superfamily Megatherioidea, making them the only surviving members of that radiation.
Extant species
Subgenus
Image
Scientific name
Common name
Distribution
Bradypus
B. pygmaeus
Pygmy three-toed sloth
Isla Escudo de Veraguas (Panama)
B. tridactylus
Pale-throated sloth
Part of northern South America, including Guyana, Suriname, French Guiana, eastern Venezuela and Brazil north of the Amazon River
B. variegatus
Brown-throated sloth
Central America and much of north and central South America, from Honduras through Colombia, Venezuela, Ecuador, eastern Peru, Bolivia and Brazil
Scaeopus
B. torquatus
Northern maned sloth
Atlantic coastal rainforest of southeastern Brazil
B. crinitus
Southern maned sloth
Coastal Brazil in Rio de Janeiro and Espírito Santo.
Evolution
A study of mitochondrial cytochrome b 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.
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 somewhat larger and generally faster-moving two-toed sloth will jointly predominate. Although similar in overall appearance, the two genera are placed in different families. Recent phylogenetic analyses support the...
