A study of retrovirus and mitochondrial DNA suggests that C. didactylus and C. hoffmani diverged 6 to 7 million years ago.

[7] Furthermore, based on cytochrome c oxidase subunit I sequences, a similar divergence date (c. 7 million years ago) between the two populations of C. hofmanni separated by the Andes has been reported.

Recent phylogenetic analyses[10] support analysis of morphological data from the 1970s and 1980s, indicating the two genera are not closely related and adapted to their arboreal lifestyles independently.

[11] Though data has been collected on over 33 different species of sloths by analyzing bone structures, many of the relationships between clades on a phylogenetic tree were unclear.

[13] Most morphological studies have concluded that convergent evolution is the mechanism that resulted in today's two genera of tree sloths.

[3][4] The following sloth family phylogenetic tree is based on collagen and mitochondrial DNA sequence data (see Fig.

[note 1] Members of Choloepus are larger than three-toed sloths, having a body length of 58 to 70 centimetres (23 to 28 in), and weighing 4 to 8 kilograms (8.8 to 17.6 lb).

[15][16] Being predominantly nocturnal, their fur, which grows greenish algae to blend in, is their main source of protection.

[19] They eat primarily leaves, but also shoots, fruits, nuts, berries, bark, some native flowers, and even some small vertebrates.

[14] Depending on when in the excretion cycle a sloth is weighed, urine and feces may account for up to 30% of the animal's body weight.

[citation needed] Two-toed sloths have a reduced, ever growing dentition, with no incisors or true canines, which overall lacks homology with the dental formula of other mammals.

Additionally, a specific section of their anterior temporalis is arranged vertically, to allow them to sharpen their caniniform teeth.