There are six living sloth, four anteater, and 20 species of armadillos. A recent study confirmed that the Andean hairy armadillo (Chaetophractus nationi) is a synonym of (i.e., the same species as) the screaming hairy armadillo (C. vellerosus), which reduced the number of extant armadillo species from 21 to 20. Paleontological records suggest that all xenarthrans originated in South America, and the distributions of all current and extinct species have been confined to specific regions of the Americas, primarily South America. A few can be found in Central America, but only one species, the nine-banded armadillo (Dasypus novemcinctus), is present in the southern United States.
These 30 extant species represent only a small fragment of a much more diverse fossil assemblage that includes such famous oddities as the giant ground sloths and glyptodonts. Current molecular evidence indicates that the Xenarthra represent one of the four major clades of placental mammals.
Two distinct groups are enclosed within Xenarthra:
- The Cingulata, which include all modern-day armadillos. They can be easily identified by the bony armor that covers their head, body, and tail (except in armadillos of the genus Cabassous, which have a naked tail). Although all armadillos feed on insects, some species also eagerly ingest other food items, such as plants, small vertebrates, or even carrion.
- The Pilosa comprise two groups:
- Vermilingua, or anteaters: their most prominent feature is a long snout and a long, prehensile tongue that helps them capture ants and termites, their preferred prey. Anteaters lack teeth.
- Folivora (= Tardigrada or Phyllophaga), or sloths: modern sloths live almost exclusively in trees, while the large, prehistoric forms were terrestrial. Sloths are famous for their slow movements and uncanny ability to hide in the tree canopy. All extant sloths feed on plants.
- Pangolins and aardvarks were historically grouped with anteaters, sloths and armadillos into a group called Edentata (=toothless). Molecular studies, however, confirmed that xenarthrans, pangolins and aardvarks are not closely related and evolved independently. Instead, their anatomical similarity represents an outstanding example of convergent evolution that reflects their common dietary specialization on colonial insects. Pangolins have been placed in a separate Order called Pholidota, while aardvarks now form the Order Tubulidentata.
We invite you to explore the world of armadillos, sloths and anteaters. In the following pages, you will find information on their biology, distribution, and conservation status, as well as the threats these charismatic animals are facing.