Edentate

Xenarthra Fossil range: Middle Paleocene - Recent
Hoffmann\'s Two-toed Sloth
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Infraclass: Eutheria Superorder: Xenarthra Cope, 1889
Orders and suborders
Order Cingulata Order Pilosa Suborder Folivora Suborder Vermilingua See text for more details

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 North America is explained by the Great American Interchange.

Evolutionary relationships

It includes the anteaters, sloths, and armadillos. In the past, these families were classified together with the pangolins and Aardvark 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 and Folivora (previously Tardigrada), and the separate order Cingulata. Xenarthra now has the rank of cohort or super-order. The Xenarthra are part of the super-cohort Atlantogenata.

Classification

SUPERORDER XENARTHRA

• Order Cingulata
  • Family Dasypodidae: armadillos
    • Pink Fairy Armadillo, Chlamyphorus truncatus
    • Pichiciego, Chlamyphorus retusus
    • Northern Naked-tailed Armadillo, Cabassous centralis
    • Chacoan Naked-tailed Armadillo, Cabassous chacoensis
    • Southern Naked-tailed Armadillo, Cabassous unicinctus
    • Greater Naked-tailed Armadillo, Cabassous tatouay
    • Little Hairy armadillo or Screaming Hairy armadillo, Chaetophractus vellerosus
    • 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
• 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
      • Hoffman\'s Two-toed Sloth, Choloepus hoffmanni
      • Southern Two-toed Sloth, Choloepus didactylus
  • 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

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