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95mya Xenarthrans

Xenarthra (from Ancient Greek xénos, “foreign, alien” and árthron, “joint”) is a major clade of placental mammals native to the Americas. There are 31 living species: the anteaters, tree sloths, and armadillos. Extinct xenarthrans include the glyptodontspampatheres and ground sloths. Xenarthrans originated in South America during the late Paleocene about 60million years ago but our common ancestry with them goes back 95 million years. They evolved and diversified extensively in South America during the continent's long period of isolation in the early to mid Cenozoic Era. Nearly all of the formerly abundant megafaunal xenarthrans became extinct at the end of the Pleistocene.

Xenarthrans share several characteristics not present in other placental mammals, which suggest their ancestors were subterranean diggers for insects. The name Xenarthra derives from the two ancient Greek words xénos, meaning "strange, unusual", and árthron, meaning "joint", and refers to their vertebral joints, which have extra articulations that are unlike other mammals. The ischium of the pelvis is also fused to the sacrum of the spine. Their limb bone structures are unusual, and they have single-color vision. The teeth of Xenarthrans are unique. Xenarthrans are also often considered to be among the most primitive of placental mammals. Females show no clear distinction between the uterus and vagina, and males have internal testicles, which are located between the bladder and the rectum. Xenarthrans have the lowest metabolic rates among therians.

Xenarthran forms and lifestyles include:

Armadillos: Mostly small and some larger omnivores and insectivores with flexible banded body armorGlyptodonts: Large herbivores with a rigid semi-spherical carapacePampatheres: Large herbivores (and possibly omnivores) with banded body armorAnteaters: Small to large specialized feeders on social insectsTree sloths: Medium-sized folivores specialized for life hanging upside-down in treesGround sloths: Medium to very large ground-living herbivores (and possibly omnivores)Aquatic sloths: Thalassocnus, a medium-sized herbivore, is the only known aquatic sloth

Ancestor's Trail
  1. Ancestor's Trail Hike
  2. Why Is Life On Earth Carbon-Based?
  3. Metazoans
  4. 900MYA we had a common ancestry with Choanoflagellates (non-animal eucaryotes)
  5. 800mya we had a common ancestry with Sponges
  6. 780mya we had a common ancestry with Placozoans
  7. 730mya Ctenophores
  8. 680mya Cnidarians
  9. 630mya Flatworms
  10. 590mya Protosomes
  11. 570mya Ambulacrarians
  12. 565mya Tunicates
  13. 560mya Cephalocordates
  14. 530mya Agnatha
  15. 460mya Chondrichthyes
  16. 440-450mya FIRST GREAT EXTINCTION
  17. 440mya Actinopterygii
  18. 417mya Dipnoi
  19. 360-375mya SECOND GREAT EXTINCTION
  20. 340mya Amphibians
  21. 310mya Sauropsids (lizard-faced non-mammalian chordates)
  22. 251mya THIRD GREAT EXTINCTION
  23. 205mya FOURTH GREAT EXTINCTION
  24. 180mya Monotremes
  25. 140mya Marsupials
  26. 105mya Afrotheres
  27. 95mya Xenarthrans
  28. 85mya Laurasiatheres
  29. 75mya Glires (Rodents and Lagomorphs)
  30. 70mya Non-primate Eurachonta (Cologus and Tree shrews)
  31. 65mya FIFTH GREAT EXTINCTION
  32. 63mya Prosimians
  33. 58mya Tarsiers
  34. 40mya Platyrrhini
  35. 25mya Catarrhini
  36. 18mya Lesser Apes
  37. 14mya Orangutans
  38. 7mya Gorillas
  39. 6mya Chimpanzees and Bonobos
  40. Human Evolution on the Ancestor's Trail
  41. 7 BILLION HUMANS