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Pilosa
The order Pilosa is a group of placental mammals, extant today only in the Americas. It includes the anteaters and sloths, including the extinct ground sloths, which went extinct about 20,000 years ago. The name comes from the Latin word for "hairy". Pilosans are good examples of ecological harmony. Anteaters, for example, feed lightly and for a short time at any one ant or nest, allowing the colony to regrow easily. Also, sloths' fur is home to many insects, as well as a type of algae that helps camouflage the sloths.
== Origins and taxonomy ==
The biogeographic origins of the Pilosa are still unclear,〔A proposed clade, Atlantogenata, would include Xenarthra and early African mammals.〕 but they can be traced back in South America as far as the early Paleogene (about 60 million years ago, only a short time after the end of the dinosaur era). The presence of these animals in Central America and their former presence in North America is a result of the Great American Interchange. A number of sloths were also formerly present on the Antilles, which they reached from South America by some combination of rafting or floating with the prevailing currents.
Together with the armadillos, which are in the order Cingulata, pilosans are part of the larger superorder Xenarthra, a defining characteristic of which is the presence of xenarthrals (extra formations between lumbar vertebrae). In the past, Pilosa was regarded as a suborder of the order Xenarthra, while some more recent classifications regard Pilosa as an order within the superorder Xenarthra. Earlier still, both armadillos and pilosans were classified together with pangolins and the aardvark as the order Edentata (meaning toothless, because the members do not have front incisor teeth or molars, or have poorly developed molars). Edentata was subsequently realized to be polyphyletic; it contained unrelated families and was thus invalid.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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