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Early Mesozoic Era: Life and Evolution

Explore the diverse flora and fauna of the Early Mesozoic Era, from marine life to land-dwelling dinosaurs. Learn why dinosaurs became dominant and how new species evolved. Discover the geological events that shaped this fascinating period.

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Early Mesozoic Era: Life and Evolution

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  1. Chapter 16 Early Mesozoic Era

  2. Guiding Questions • What groups of animals were conspicuous in Triassic and Jurassic seas? • What kinds of plants played major roles on land in early Mesozoic time? • Why did dinosaurs replace therapsids as the dominant vertebrate animals on land? • What groups of vertebrate animals evolved the ability to fly during early Mesozoic time?

  3. 145 Million years 202 Million years 251 Million years

  4. Early Mesozoic • Bounded by mass extinctions • Recovery from Permian mass extinction of: • Fusulinids • Lacy bryozoans • Rugose corals • Trilobites

  5. Early Mesozoic Life • Mollusks are abundant • Ammonoids • 2 genera diversity to 100 • Stromatolites returned to shallow water • Bivalves abundant • Sea urchins

  6. Early Mesozoic Life • Reefs • Hexacorals • Dominant reef builder • Some resemble rugose corals

  7. Early Mesozoic Life • Pelagic Realm • Dinoflagellates • Calcareous nannofossils • Ammonoids • Rapid evolution • 1 million year range

  8. Early Mesozoic Life • Belemnoids • Squid-like relatives of Ammonoids • Ammonoids were important guide fossils

  9. Early Mesozoic Life • Fishes - More modern - Scales covered bodies - Skeletons of cartilage - Simple Jaws - Peg-like teeth

  10. Early Mesozoic Life • Marine reptiles • Placodonts • Blunt-toothed shell crushers • Broad armored bodies

  11. Early Mesozoic Life • Marine reptiles • Nothosaurs • Early Triassic • May be first marine reptiles

  12. Early Mesozoic Life • Plesiosaurs • Evolved from nothosaurs

  13. Early Mesozoic Life • Ichthyosaurs • Fish lizards • Bore live young

  14. Early Mesozoic Life on Land • Tree-forming Gymnosperms • Cycads • Cycadeoids • Ginkgos

  15. Early Mesozoic Life on Land • Mesozoic forests looked very different from modern forests

  16. Early Mesozoic Life on Land • Early Mammals • Mammals evolved from therapsids • Small • Thecodonts • Dinosaur ancestors • Upper portion of legs extended downward rather than sprawling

  17. Early Mesozoic Life on Land • Thecodont descendents • Dinosaurs • Bipedal • Different skull • More highly developed teeth • Crocodiles

  18. Early Mesozoic Life on Land • Dinosaur evolution • Bird- hipped • Herbivores • Lizard-hipped • Herbivores • Carnivores

  19. Early Mesozoic Life on Land • Sauropods • Largest of all dinosaurs • Morrison Formation

  20. Early Mesozoic Life on Land • Allosaurus • Largest carnivore

  21. Early Mesozoic Life on Land • Pterosaurs • Long wings • Hollow bones • Flight

  22. Early Mesozoic Life on Land • Archaeopteryx • Missing link • Feathered • Breastbone

  23. Paleogeography • Pangaea began to separate

  24. Paleogeography • Tethys seaway formed • Site of modern Mediterranean

  25. Paleogeography • Rifting began first in north, then spread south

  26. Paleogeography • Salt domes • Thick evaporites built up in modern Gulf of Mexico • Formed salt domes • Petroleum reserves

  27. Triassic Mass Extinction • Global warming • Volcanic activity released high volumes of CO2 • Number of leaf stomates increased • Cells that utilize CO2

  28. Tectonic Events in Eastern U.S. • Rifting created fault basins • Evaporites accumulated as seawater leaked into basin

  29. Tectonic Events in Eastern U.S. • Basins • Filled with clastic sediments • Arkose rich • Rapid deposition

  30. Tectonic Events in Eastern U.S. • Palisades Sill • Mafic intrusion associated with rifting • Near New York City

  31. Tectonic Events in Western U.S. • Petrified Forest • Chinle formation • Utah and Arizona

  32. Tectonic Events in Western U.S. • Sundance Sea • Global sea level rose • Pacific flooded western U.S.

  33. Tectonic Events in Western U.S. • Grew by accretion of exotic terrane • Island arc terranes • Accreted Golconda Arc • Microplates • Accreted Sonomia • Southeastern Oregon • Northern California and Nevada

  34. Tectonic Events in Western U.S. • Accretion • Golconda Arc • Sonomia

  35. Tectonic Events in Western U.S. • Subduction led to intrusions • Sierra Nevada batholiths

  36. Tectonic Events in Western U.S. • Additional accretion • Accretionary wedge • Franciscan rocks • Great Valley turbidites

  37. Tectonic Events in Western U.S. • Sundance Sea • Retreated as it filled with sediments • No flysch deposition • Significant molasse • Morrison Formation

  38. Dinosaurs • Morrison Formation • Excavation of dinosaur fossils

  39. Dinosaurs • Parasauralophus • 3 m long • Resonating chamber in the head

  40. Dinosaurs • Maiosaura hatchling • 50 cm long

  41. Dinosaurs • Oviraptor • Egg stealer • small at 0.7 m in size

  42. Dinosaurs • Protoarchtopterix • Precursor of feathers • 60 cm in size

  43. Dinosaurs • Protoarchaeopteryx • Fossilized tail feathers

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