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Chapter 16

Chapter 16. Early Mesozoic Era. 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?

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Chapter 16

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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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