What is a xenarthran?

Xenarthrans are an ancient group of mammals that includes armadillos (order Cingulata) and sloths and anteaters (order Pilosa). A unique characteristic of xenarthrans is the presence of extra joints in their lower back vertebrae, which strengthens their hips and lower back. This adaptation assists them in using their forelegs for activities like digging, which is how anteaters and armadillos primarily get their food. Xenarthrans have low metabolisms compared to other mammals, resulting in lower body temperatures and reduced food intake. While xenarthrans were once grouped with pangolins and called edentates, referring to the absence of teeth in some members, the moniker is no longer accurate. Today, xenarthrans are only located in the Western Hemisphere; however, their historical range was far more diverse.

Which animals are included in the xenarthran group?

Xenarthra is an ancient group of mammals found only in the Western Hemisphere. The animals included in Xenarthra are the armadillos (order Cingulata) and the sloths and anteaters (order Pilosa). Xenarthrans share a unique feature in their lower backbones, which have extra joints that strengthen the lower back and hips. This adaptation helps them use their forelegs for activities like digging, which is how anteaters and armadillos find food.

Where do xenarthrans live in the world today?

Today, xenarthrans are found only in the Western Hemisphere. This group of mammals includes armadillos , sloths , and anteaters . Sloths live in the lowland tropical areas of South and Central America. Anteaters inhabit tropical savannas and forests from southern Mexico to Paraguay and northern Argentina. Most armadillo species live in open areas of tropical and subtropical regions of Central and South America, though the nine-banded armadillo's range extends into the southern United States.

What special features do xenarthrans have that set them apart from other mammals?

Xenarthrans are an ancient group of mammals that includes armadillos , sloths , and anteaters . A defining feature is the presence of extra joints (arthroses) in their lumbar vertebrae, which strengthens their lower back and hips. This adaptation aids in activities like digging, which is essential for anteaters and armadillos in obtaining food. Xenarthrans have a low metabolism compared to other mammals, resulting in lower body temperatures and reduced food intake. Their diets vary, ranging from the insectivorous anteaters to the folivorous sloths, while armadillos consume both plant matter and small animals. Xenarthrans are only found in the Western Hemisphere, with the exception of the nine-banded armadillo, which can be found in the southern United States.

How do xenarthrans obtain their food and what do they eat?

Xenarthrans, an ancient group of mammals, have diverse feeding strategies based on their specific diets. Anteaters are strictly insectivorous, using their strong claws to tear open insect nests and their long, sticky tongues to capture ants and termites. Armadillos consume a variety of plant matter, small animals, and insects, which they locate with their keen sense of smell. Sloths, spend most of their time in trees where they eat leaves, twigs, flowers, and other foliage, though some species may eat insects and other small animals. These mammals have low metabolisms, eating less and maintaining cooler body temperatures compared to other mammals.

xenarthran

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A tamandua, or lesser anteater, extends its long tongue. Overlaid text reads "16 inch TONGUE" with an arrow pointing to the tongue. Forest background.

Observe the three-toed sloth eating foliage and moving about in its natural habitat, the tropical forest canopy

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Related Topics:: sloth; armadillo; anteater; Pilosa; Cingulata

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xenarthran

mammal

Also known as: Xenarthra

Written by

Alfred L. Gardner

Fact-checked by

Britannica Editors

History

Top Questions

What is a xenarthran?
Xenarthrans are an ancient group of mammals that includes armadillos (order Cingulata) and sloths and anteaters (order Pilosa). A unique characteristic of xenarthrans is the presence of extra joints in their lower back vertebrae, which strengthens their hips and lower back. This adaptation assists them in using their forelegs for activities like digging, which is how anteaters and armadillos primarily get their food.

Xenarthrans have low metabolisms compared to other mammals, resulting in lower body temperatures and reduced food intake. While xenarthrans were once grouped with pangolins and called edentates, referring to the absence of teeth in some members, the moniker is no longer accurate. Today, xenarthrans are only located in the Western Hemisphere; however, their historical range was far more diverse.
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1. xenarthran
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Which animals are included in the xenarthran group?
Xenarthra is an ancient group of mammals found only in the Western Hemisphere. The animals included in Xenarthra are the armadillos (order Cingulata) and the sloths and anteaters (order Pilosa). Xenarthrans share a unique feature in their lower backbones, which have extra joints that strengthen the lower back and hips. This adaptation helps them use their forelegs for activities like digging, which is how anteaters and armadillos find food.
1 Britannica Source
1. xenarthran
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Where do xenarthrans live in the world today?
Today, xenarthrans are found only in the Western Hemisphere. This group of mammals includes armadillos, sloths, and anteaters.

Sloths live in the lowland tropical areas of South and Central America. Anteaters inhabit tropical savannas and forests from southern Mexico to Paraguay and northern Argentina. Most armadillo species live in open areas of tropical and subtropical regions of Central and South America, though the nine-banded armadillo's range extends into the southern United States.
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Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What special features do xenarthrans have that set them apart from other mammals?
Xenarthrans are an ancient group of mammals that includes armadillos, sloths, and anteaters. A defining feature is the presence of extra joints (arthroses) in their lumbar vertebrae, which strengthens their lower back and hips. This adaptation aids in activities like digging, which is essential for anteaters and armadillos in obtaining food.

Xenarthrans have a low metabolism compared to other mammals, resulting in lower body temperatures and reduced food intake. Their diets vary, ranging from the insectivorous anteaters to the folivorous sloths, while armadillos consume both plant matter and small animals. Xenarthrans are only found in the Western Hemisphere, with the exception of the nine-banded armadillo, which can be found in the southern United States.
1 Britannica Source
1. xenarthran
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How do xenarthrans obtain their food and what do they eat?
Xenarthrans, an ancient group of mammals, have diverse feeding strategies based on their specific diets. Anteaters are strictly insectivorous, using their strong claws to tear open insect nests and their long, sticky tongues to capture ants and termites. Armadillos consume a variety of plant matter, small animals, and insects, which they locate with their keen sense of smell. Sloths, spend most of their time in trees where they eat leaves, twigs, flowers, and other foliage, though some species may eat insects and other small animals.

These mammals have low metabolisms, eating less and maintaining cooler body temperatures compared to other mammals.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

xenarthran, an ancient lineage of mammals comprising the armadillos (order Cingulata) and the sloths and anteaters (order Pilosa). The namesake feature shared by all members of Xenarthra is seen in the lower backbone. The lumbar vertebrae are “xenarthrous”; that is, they have extra contacts (joints, or arthroses) that function to strengthen the lower back and hips. This aids use of the forelegs in activities not associated with locomotion, such as digging—the primary method used by anteaters and armadillos to obtain food.

Xenarthran diets range from strictly insectivorous in anteaters, which eat only ants and termites, to strictly folivorous in sloths, which eat only leaves. Armadillos, not nearly as specialized, eat a variety of plant matter and small animals. Xenarthran metabolisms, however, are similar in that all are low compared with those of other mammals; some burn calories at less than half the rate expected for mammals of similar size. As a result, xenarthrans eat less than other mammals and have body temperatures that are a few degrees cooler.

Present distribution of xenarthrans is restricted to Latin America, the exception being the nine-banded armadillo (Dasypus novemcinctus), whose range extends into the southern United States.

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Cingulata

GlyptodontGlyptodont (genus *Glyptodon*).

Order Cingulata consists primarily of armoured armadillo-like animals, and the name refers to the girdlelike shell of present-day armadillos. The armadillo family (Dasypodidae), with 8 genera and 20 species, is the only surviving family of Cingulata. Five other families in this order are extinct and are known only from fossil remains. Members of extinct families include glyptodonts and huge North American armadillos.

Pilosa

silky anteaterSilky anteater (*Cyclopes didactylus*) extending its long, narrow tongue, which it uses to capture and ingest prey.

Sloths and anteaters are the living members of the order Pilosa, whose name refers to the animals’ hairiness. Three families exist today, encompassing five genera and nine species. Six families, primarily ground sloths, are extinct. The order Pilosa is further subdivided into the suborder Vermilingua, literally “worm-tongue,” which is descriptive of the long slender tongue of anteaters, and the suborder Phyllophaga, meaning “leaf-eater,” descriptive of the diet of sloths.

Paleontology and classification

Xenarthrans are known only from the Western Hemisphere and arose in South America during the Paleocene Epoch (65.5 million to 55.8 million years ago). The fossil record shows that the group was both more diverse and more widely distributed as recently as the Pleistocene Epoch (2,600,000 to 11,700 years ago), when ground sloths colonized the islands of the Greater Antilles and glyptodonts, ground sloths such as Megatherium, and giant armadillos roamed North America. At least one species of ground sloth reached present-day Alaska.

Magnorder Xenarthra
29 species among five living families. Xenarthrans were formerly grouped with pangolins and collectively referred to as edentates (order Edentata), which alludes to the absence of teeth in some members.
- Order Cingulata
  - Family Dasypodidae (armadillos)
    20 species in eight genera
- Order Pilosa
  - Suborder Vermilingua (anteaters)
    Four species in two families
    - Family Myrmecophagidae
      Three species in two genera
    - Family Cyclopedidae
      One species
  - Suborder Phyllophaga (sloths)
    Five species in two families
    - Family Megalonychidae (two-toed sloths)
      Two species in one genus
    - Family Bradypodidae (three-toed sloths)
      Three species in one genus

Alfred L. Gardner

xenarthran

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Cingulata

Pilosa

Paleontology and classification