Mesozoic Era: Age of Reptiles

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Mesozoic EraAge of Reptiles

• Chapter 13, Section 3

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Mesozoic History

• The Mesozoic era spanned about 183 million years,
  and it is divided into three periods the
  Triassic, Jurassic, and Cretaceous
• The Mesozoic era began with much of the worlds
  land above sea level (very few marine fossils are
  found in North America from the Triassic Period)
• In the Cretaceous, shallow seas invaded much of
  western North America creating great swamps
  (leaving large coal deposits)
• A major event of the Mesozoic era was the breakup
  of Pangaea
• This process lasted for 200 million years,
  forming the Atlantic Ocean
• It also caused the North American plate to
  override the Pacific plate, causing massive
  deformation, forming the Sierra Nevada and Rocky
  Mountains

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The Breakup of Pangaea
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Concept Check

• Explain how the Atlantic Ocean was formed.
• A rift developed during the breakup of a Pangaea
  that widened and eventually became the Atlantic
  Ocean.

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Mesozoic Life

• When the Mesozoic began, its life forms were the
  survivors of the great Paleozoic extinction
• Gymnosperm seed-bearing plant that bears its
  seeds on the surface of cones
• Unlike the first plants to invade land,
  gymnosperms were not restricted to living near
  the waters edge, and they could take advantage
  of nutrients and space available in drier areas
• The gymnosperms quickly became the dominant
  plants of the Mesozoic
• Gymnosperm trees included the cycads, the
  conifers, and the ginkgoes
• Among the animals, reptiles readily adapted to
  the drier Mesozoic environment, being the first
  true land animals

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Gymnosperms
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Reptiles Dominate

• With the perfection of the shelled egg, reptiles
  quickly became the dominant land animals
• They continued this dominance for 160 million
  years
• Dinosaur land-dwelling reptile of the Mesozoic
  era
• The reptiles made an amazing adaptation, one
  previously made by insects, they began to fly
  (the pterosaurs)
• Another group of reptiles led to the more
  successful flyersthe birds
• Some reptiles also returned to the sea, but
  retained their reptile teeth and breathed with
  their lungs
• At the end of the Mesozoic, many reptile groups
  became extinct
• Only a few types of reptiles survived to recent
  times (the turtles, snakes, crocodiles, and
  lizards)
• Most scientists believe that the extinction of
  the large reptiles was caused by a large
  meteorite that collided with Earth

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Reptile Evolution
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PteranodonThe Flying Reptile
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Concept Check

• How did reptiles become the dominant land
  animals?
• The development of shelled eggs allowed dinosaurs
  and other reptiles to dominate the land.

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Assignment

• Read Chapter 13, Section 3 (pg. 377-381)
• Do Section 13.3 Assessment 1-5 (pg. 381)
• Print Out Investigation 13 Determining
  Geologic Ages"