Mesozoic

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Mesozoic

• Three time periods
• Triassic
• (245-208 Ma)
• Jurassic
• (208-146 Ma)
• Cretaceous
• (146-65 Ma)

Cretaceous world (80 Ma) From Paleomap Project -
Scotese.com
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Paleo-Meso Timeline

• Land Plants Ordovician (seeds by Devonian)
• Air-breathing arthropods - Silurian
• Amphibians - Devonian, abundant in early
  Carboniferous
• Reptiles - Later Carboniferous

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Paleo-Meso Timeline

• Permo-Triassic - huge extinction
• Sea level fall
• Continents locked up in Pangea in the Southern
  Hemisphere
• Ice caps cover Antarctica, parts of Australia,
  Southern parts of Africa and South America
  (Gondwanaland)

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Paleo-Meso Timeline

• Dinosaurs - Triassic
• Mammals - Triassic
• Birds - Jurassic
• Ammonites become dominant - Jurassic
• Ammonites, Dinosaurs rule all - Cretaceous
• Flowering plants - Cretaceous

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Paleo-Meso Timeline

• Tectonics
• Pangea to present (Scotese.com)
• http//scotese.com/sfsanim.htm
• Variety of animations (UCMP)
• http//www.ucmp.berkeley.edu/geology/tectonics.ht
  ml

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Big changes in the MesozoicPlants

• Early Mesozoic dominated by ferns,
• cycads, ginkgophytes, and others not
• widely seen today.
• Modern gymnosperms (e.g. conifers), first
  appeared in their current recognizable forms in
  the early Triassic.
• By the middle of the Cretaceous, the earliest
  angiosperms (flowering plants) had appeared and
  began to diversify - became dominant.

Mesozoic Ginkgo
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Mesozoic Developments

• After the Triassic its warmer
• Tethys sea is opening
• Marine plants
• Dinoflagellates flourish (were around in Silurian
  and Permian, but didn't do much)
• Mineralized phytoplankton (Coccolithophorids)
  begin to bloom - great fossil record

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Mesozoic Developments

• Land Plants
• Carboniferous-Permian - big spore-bearing plants
• Mesozoic - pollinating
• Early Mesozoic -Cycads, Ginkgoes, Seed Ferns,
  Conifers - seeds, but no flowers
• Cretaceous - Flowering plants (angiosperms) with
  enclosed seeds

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Mesozoic Developments

• Land Invertebrates
• Shelled - some rare air-breathing snails,
  freshwater snails and clams
• Arthropods
• Carboniferous-Permian had spiders, millipedes,
  scorpions, centipedes
• Added in Mesozoic are flies, mosquitoes, earwigs,
  wasps, bees, ants and beetles
• Not yet - Butterflies, moths, termites, fleas

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Mesozoic Developments

• Marine Invertebrates
• Big Permian extinction
• Slower rebound - not until middle Triassic
• Pelecypods expanded, eventually outdid
  brachiopods - especially oysters
• Rudists - horn-shaped shells, formed reefs just
  like corals did

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Mesozoic Developments

• Marine Invertebrates
• Corals - same as today, with same requirements
  (zooxanthellae)
• Echinoids
• Ammonoids - good index fossils because of suturing

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End of Mesozoic
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End of Mesozoic

• Cretaceous-Tertiary boundary marks a mass
  extinction
• 20-25 of all extant families died out completely
• What evidence is there for a cause?
• Iridium layer
• Shocked quartz
• Glassy spherules - tektites
• Soot from burning

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End of Mesozoic

• Regular Quartz

• Shocked Quartz

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End of Mesozoic

• Crater formation animation
• http//www.lpl.arizona.edu/SIC/impact_cratering/C
  hicxulub/Animation.gif

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Chixulub Yucatan Peninsula
Wrong place, wrong shoreline, cool picture
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End of Mesozoic

• Most accepted hypothesis
• Bolide impact - a big object from space smashes
  into the Earth, causing mass destruction
• Chixulub - big crater in the Yucutan peninsula of
  Mexico
• appears to be approximately the right age

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End of Mesozoic

• Other effects of impact
• Forest fires
• Tsunamis

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End of Mesozoic

• Alternate hypotheses
• Rain of comets -
• Planet X dislodges comets in Oort cloud
• Periodicity of extinctions about 26 million years
• No evidence
• Cosmic rays from a nearby supernova
• Doesnt explain impact-related features
• Why extinctions in ocean, then?

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End of Mesozoic

• Alternate hypotheses -
• Terrestrial explanations
• Sea level drop - less plate activity
• Volcanoes
• How instantaneous was it?
• Not all extinctions happened at end of Cretaceous
  some predate it. That hinders the impact
  hypothesis, unless the dinosaurs were psychic.