First major extinction

65mya FIFTH GREAT EXTINCTION

DINOSAURS WENT EXTINCT!
Cretaceous–Tertiary extinction event (End Cretaceous or K-T extinction) - 70 to 65 Ma at the Cretaceous.Maastrichtian-Paleogene.Danian transition interval. The K–T event is now called the Cretaceous–Paleogene (or K–Pg) extinction event by many researchers. About 17% of all families, 50% of all genera and 75% of species went extinct. In the seas it reduced the percentage of sessile animals to about 33%. The boundary event was severe with a significant amount of variability in the rate of extinction between and among different clads. Mammals and birds emerged as domininant land vertebrates in the age of new life.

As originally proposed in 1980 by a team of scientists led by Luis Alvarez and his son Walter, it is now generally thought that the K–Pg extinction was caused by the impact of a massive comet or asteroid 10 to 15 km (6 to 9 mi) wide, 66 million years ago, which devastated the global environment, mainly through a lingering impact winter which halted photosynthesis in plants and plankton. The impact hypothesis, also known as the Alvarez hypothesis, was bolstered by the discovery of the 180 km Chicxulub crater in the Gulf of Mexico's Yucatán Peninsula in the early 1990s, which provided conclusive evidence that the K–Pg boundary clay represented debris from an asteroid impact.

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