Bradypodidae (tree sloths; infra-order Pilosa, superfamily Bradypodoidea)
A family of toothless mammals that are fully adapted for arboreal life and unable to walk on the ground; they use their limbs to hang upside-down from branches. The head is short and rounded. They are not actually toothless, but the five teeth have no enamel and by growing continuously provide a grinding surface. The fore limbs are longer than the hind limbs, the digits bearing hooked claws used in hanging. The tail is short. The fur is long, coarse, and grooved; cyanobacteria grow in the grooves, giving the animals a greenish colour. There are six cervical vertebrae in Choloepus
, nine in Bradypus
. The stomach is large and chambered, the rectum very large, retaining faeces for several days. All movements are slow. The body temperature
is low and variable, sloths neither shivering nor sweating, but dying from hypothermia at temperatures below 4°C. They are distributed throughout the forests of tropical America. There are two genera, and five species.