Introduction to the Xenarthra

anteaters, armadillos, and sloths

Three-toed Sloth
Three-toed Sloth. Photo by Dr. Llloyd Glenn Ingles, © 2001 California Academy of Sciences.

Anteaters, armadillos, and sloths are a group of eutherian mammals known as the Xenarthra. They were once placed in the order Edentata and are still often referred to as edentates, a word that means "toothless." Although xenarthrans such as anteaters are indeed toothless, the giant armadillo has as many as 100 teeth, more than almost any other mammal. Members of the mammalian group Edentata not only include the 31 living species of armadillos, true anteaters, and tree sloths, but also contain eight families of extinct ground sloths and armadillo-like animals. Together, the living families and extinct families constitute the Xenarthra.

Xenarthrans are a small group of insectivores and herbivores of small to medium body size (up to around 60 kg). In the past however, xenarthrans were much more diverse and numerous. They radiated into about a dozen families in South America, including not only the groups known today but also animals such as the extinct giant ground sloths and giant armored gylptodonts. Several groups of xenarthrans, mainly the ground sloths and armadillos, successfully crossed the Central American land bridge to North America when it formed during the Pliocene. Today, only one of these species, an armadillo (Dasypus novemcinctus),
Six-banded Armadillo
Six-banded Armadillo. Photo by Gerald and Buff Corsi, © 2001 California Academy of Sciences.
still survives there; the majority of living species live in Central and South America.

Read about living xenarthrans at the University of Michigan's Animal Diversity Web.

Visit Sloth World, an online bibliography and database of sloth papers from around the world maintained by Robert McAfee.

The Bibliography on Armadillos, compiled by Mariella Superina, lists hundreds of articles published on that group, and even covers papers published before 1900!


  • Anderson, S., and J.K. Jones, Jr. (eds.). 1984. Orders and Families of Recent Mammals of the World. Wiley, New York.
  • Dickson, C.R. 1984. Edentates. Pp. 770–783 in David MacDonald (ed.). Encyclopedia of Mammals. Facts on File, Inc., New York.
  • Eisenberg, J.F. 1981. The Mammalian Radiations: An Analysis of Trends in Evolution, Adaptation, and Behavior. University of Chicago Press, Chicago.
  • Gunderson, H.L. 1976. Mammalogy. McGraw-Hill, New York.

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