Xenarthra

The superorder Xenarthra is a group of placental mammals (infraclass Eutheria), extant today only in the Americas. The origins of the order can be traced back as far as the early Tertiary (about 60 million years ago, shortly after the Mesozoic era). The presence of these animals in Central and North America is explained by the Great American Interchange.

Xenarthrans have the lowest metabolic rates among the therians.

Evolutionary relationships

Xenarthra includes the anteaters, tree sloths, and armadillos, as well as the extinct ground sloths, glyptodonts and pampatheres. In the past, these families were classified together with the pangolins and aardvarks as the order Edentata (meaning toothless, because the members do not have front incisor teeth or molars, or have poorly-developed molars). It was subsequently realized that Edentata was polyphyletic—that it contained unrelated families and was thus invalid by cladistic standards. Aardvarks and pangolins are now placed in individual orders, and the new order Xenarthra was erected to group the remaining families (which are all related). The name Xenarthra means "strange joints", and was chosen because their vertebral joints have extra articulations and are unlike those of any other mammals. Because they lack characteristics believed to be present in the common ancestor of other known eutherian mammals, morphological evidence suggests that the Xenarthra are outside the Epitheria, which contains all other known eutherians today.

The morphology of xenarthrans generally suggests that the anteaters and sloths are closest together within Xenarthra, which is upheld by molecular studies. The order Xenarthra is more and more often divided into two orders: Pilosa, containing the Vermilingua (anteaters) and Folivora (sloths; previously known as Tardigrada or Phyllophaga), and the separate order Cingulata (armadillos). Xenarthra now has the rank of cohort or super-order. The Xenarthra are part of the super-cohort Atlantogenata.

Xenarthra may be most closely related to either Afrotheria (in the group Atlantogenata), or Epitheria (comprising Afrotheria and Boreoeutheria). In other words it may be nested within Eutheria or it may be the basal extant group. A comprehensive phylogeny by Goloboff et al. includes Xenarthrans as a sister clade of Boreoeutheria (Euarchontoglires+Laurasiatheria).

Classification

SUPERORDER XENARTHRA Order Cingulata
Family Dasypodidae: armadillos
Pink Fairy Armadillo, Chlamyphorus truncatus
Northern Naked-tailed Armadillo, Cabassous centralis
Chacoan Naked-tailed Armadillo, Cabassous chacoensis
Southern Naked-tailed Armadillo, Cabassous unicinctus
Greater Naked-tailed Armadillo, Cabassous tatouay
Screaming Hairy Armadillo, Chaetophractus vellerosus
Big Hairy Armadillo, Chaetophractus villosus
Andean Hairy Armadillo, Chaetophractus nationi
Nine-banded Armadillo or Long-nosed Armadillo, Dasypus novemcinctus
Seven-banded Armadillo, Dasypus septemcinctus
Southern Long-nosed Armadillo, Dasypus hybridus
Llanos Long-nosed Armadillo, Dasypus sabanicola
Great Long-nosed Armadillo, Dasypus kappleri
Hairy Long-nosed Armadillo, Dasypus pilosus
Six-banded Armadillo or Yellow Armadillo, Euphractus sexcinctus
Giant Armadillo, Priodontes maximus
Southern Three-banded Armadillo, Tolypeutes matacus
Brazilian Three-banded Armadillo, Tolypeutes tricinctus
Pichi or Dwarf Armadillo, Zaedyus pichiy
Family †Glyptodontidae: glyptodonts
Family †Pampatheriidae: pampatheres
Order Pilosa
Suborder Folivora
Family Bradypodidae: three-toed sloths
Pygmy Three-toed Sloth, Bradypus pygmaeus
Brown-throated Three-toed Sloth, Bradypus variegatus
Pale-throated Three-toed Sloth, Bradypus tridactylus
Maned Three-toed Sloth, Bradypus torquatus
Family Megalonychidae: two-toed sloths and extinct megalonychid ground sloths
Hoffman's Two-toed Sloth, Choloepus hoffmanni
Linnaeus's Two-toed Sloth or Southern Two-toed Sloth, Choloepus didactylus
Family †Megatheriidae: megatheriid ground sloths
Family †Mylodontidae: mylodontid ground sloths
Family †Orophodontidae: orophodontid ground sloths
Suborder Vermilingua
Family Cyclopedidae: silky anteaters
Silky Anteater, Cyclopes didactylus
Family Myrmecophagidae: anteaters
Giant Anteater, Myrmecophaga tridactyla
Northern Tamandua, Tamandua mexicana
Southern Tamandua, Tamandua tetradactyla

Translation

The word "Xenarthra" occurs as such in the following languages: English, Breton, Spanish, French, Croatian, Italian, Latin, Maltese, Dutch, Occitan, Portuguese, Simple English, Thai.

Translation(s) in other languages: Arabic: لاضرسيات, Bulgarian: Непълнозъби, Catalan: Xenartre, Czech: Chudozubí, Danish: Gumlere, German: Nebengelenktiere, Esperanto: Ksenartroj, Faroese: Jagldýr, Korean: 빈치류, Icelandic: Tannleysingjar, Hebrew: דלשינאים, Georgian: არასრულკბილიანები, Lithuanian: Nepilnadančiai, Limburgian: Tanderme, Hungarian: Vendégízületesek, Macedonian: Чуднозглобни, Japanese: 異節上目, Norwegian (Bokmål): Gomlere, Polish: Szczerbaki, Russian: Неполнозубые, Finnish: Vajaahampaiset, Swedish: Trögdjur, Ukrainian: Неповнозубі, Chinese: 貧齒總目.