Xenarthra

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Myrmecophagidae

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Megalonychidae

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Bradypodidae

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Dasypodidae

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The order Xenarthra is a group of placental mammals, 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, or only a short time after the end of the dinosaur era). The presence of these animals in North America is explained by the Great American Interchange.

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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. 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 are unlike those of any other mammals. Because they lack characters 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.

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The morphology of Xenarthrans generally suggests that the anteaters and sloths are closest together within Xenarthra.

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• ORDER XENARTHRA
• Suborder Vermilingua
• Family Myrmecophagidae: anteaters
• Silky Anteater, Cyclopes didactylus
• Giant Anteater, Myrmecophaga tridactyla
• Northern Tamandua, Tamandua mexicana
• Southern Tamandua, Tamandua tetradactyla
• Suborder Tardigrada
• Family Bradypodidae: three toed sloths
• 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
• Ground sloth, Megalonyx jeffersonii (extinct)
• Family Megatheriidae (extinct)
• Giant ground sloth, Eremotherium laurillardi
• Family Mylodontidae (extinct)
• Suborder Cingulata
• Family Pampatheriidae
• Holmesina septrionalis
• Family Glyptodontidae (extinct)
• Glyptotherium arizonae
• Family Dasypodidae: armadillos
• About 20 species in 8 genera, not listed here.

Tertiary: The Tertiary period was previously one of the major divisions of the geologic timescale, from the end of the Cretaceous period about 65.5 million years ago to the start of the Quaternary period about 1.6 million years ago. Its use has been widespread and continues, however the International Commiss...

North America: North America is a continent in the northern hemisphere, bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the south by the Caribbean Sea, and on the west by the North Pacific Ocean. It covers an area of 9,355,000 square miles (24,230,000 square kilometers). In 2...

Great American Interchange: The Great American Interchange was a very important paleozoogeographic event in which land and freshwater animal faunas migrated from Central America to South America and vice versa, during the collision of both continents. The migration peaked dramatically around 3 Million years ago (Piacenzian, f...