Mammal Classification
Anteaters, Sloths and Armadillos
The 29 species in the order Xenarthra are linked by their South American origins and a shared anatomical feature: uncommonly strong backbones. The xenarthrans get their name from an extra articulation, called a xenarthrous process, in their lumbar vertebrae. Apart from this skeletal characteristic, the families in this order display more differences than similarities.
Anteaters live mainly in warm, moist tropical habitats. They use their long, sharp claws to tear up hard-packed nests of ants and termites, catching the insects with their long tongues, made sticky by secretions from specialized salivary glands. Although the other three species in its family are largely arboreal, the giant anteater lives a terrestrial life. Up to about four feet (1 m) in length and weighing as much as 90 pounds (40 kg), it has an awkward gait due to its large, inwardly turned, non-retractable claws. It can, however, run surprising fast when necessary.
Sloths don't do anything fast. Notorious for their low activity level, they spend most of their time hanging upside down in trees and eating leaves in their rain-forest habitat. They are so specialized for arboreal life — possessing long forelimbs, muscles evolved for hanging and long, curved claws — that they have difficulty moving on the ground. Armadillos have no such problem. Their powerful limbs make them fast runners. They get their name from the bony plates of jointed armor that cover their body, neck and head. Most of the 20 armadillo species feed primarily on insects, but will also eat small vertebrates and some vegetable matter. They can be found all over South America, and extend into North America as far as Nebraska. Prolonged cold spells have been known to wipe out about two-thirds of populations living in the more northerly habitats.
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