Review of Mesozoic Earth History

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Review of Mesozoic Earth History

• Main Happenings in Mesozoic
• Breakup of Pangaea
• Lots of mountain-building in western North
  America
• Appearance extinction of dinosaurs
• More detail in the geologic record
• More climate information!

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The hydrologic cycle and climate
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Water moves heat around the planet tectonics
determines how effectively this heat can move

• Mountains and continental shape/size determine
  whether the hydrologic cycle can transport heat
  effectively
• Mountains can block rainfall
• Massive continents tend to have dry interiors
• Coastal regions benefit from water cycle climate
  controls
• Circumpolar currents cut off polar access to warm
  waters
• N/S currents waterways moderate polar climate

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End Permian land and oceans
Panthalassa

• Pangaea was shaped like a C
• Inside ocean Tethys Sea
• Outside ocean Panthalassa

Tethys sea
Panthalassa
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Breakup of Pangea 1 Triple Junctions

• Seafloor spreading creates a triple junction a
  point where 3 tectonic plates diverge
• North America split off from S America and Africa

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Seafloor spreading raises sea level

• Seafloor spreading causes bulges in ocean basins
• Big enough bulges and/or lots of them lowers the
  ocean volume
• This can cause flooding of the continents.

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Western Interior Seaway
www.isgs.uiuc.edu/dinos/westernseaway.gif
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Cordillera Orogenies

• General term refering to complex period of
  mountain-building Jurassic-Cenozoic
• Farallon plate goes below N American plate
• Nevadan orogeny Late Jurassic/Early Cretaceous
• Orogeny near the current W coast
• Slope of subducting Farallon plate decreased -gt
• Sevier orogeny Late Cretaceous
• Further east (Utah)
• Laramide orogeny Late Cretaceous/Cenozoic
• Even FURTHER east! Rockies

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Triassic

• Arid, red beds
• Lots of fern prairies no grasses yet
• Dinosaurs first appear

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Triassic

• Dinosaurs evolved from reptiles
• Special hips and ankles that allow them to stand
  on 2 feet
• Speed, agility and less need for water gives them
  edge

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Jurassic

• Pangaea is breaking up causes SL to rise

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Jurassic

• Climate wetter than Triassic
• Forests replace deserts, still fern prairies
• Dinosaurs diverse and abundant
• Giant marine reptiles

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Cretaceous

• SL still rising as breakup of Pangaea continues
• Atlantic only about 300 km wide

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Cretaceous

• Abundant flying reptiles
• First flowers
• Birds with feathers

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Isolation

• Pangaea began fragmenting
• during the Triassic and continues to do so
• Organisms had increasing difficulty
• migrating between continents as a result
• In fact, South America and Australia
• became isolated island continents
• their faunas evolving in isolation
• became quite different from those elsewhere

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Mesozoic Marine Revolution

• Many predators in ocean
• Marine reptiles
• Fish, sharks
• Crabs, lobsters could crush shells

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Mesozoic Marine Revolution

• Many predators in ocean
• Marine reptiles
• Fish, sharks
• Crabs, lobsters could crush shells
• Marine animals had to adapt
• Burrow/hide (eg. clams, gastropods)
• Thick shells
• Swim

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Echinoderms

• Metazoans (animals) but not vertebrates or even
  chordates
• 5-fold symmetry

www.humboldt.edu/natmus/Exhibits/Life_time/Cretac
eous.web/327.jpg
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Marine Vertebrates

• Numerous bony fish
• Cephalopods most common swimming animals
• Squids, octopus, ammonites
• Marine reptiles not dinosaurs, not fish!
  Ichthyosaurs
• Plesiosaurs
• Mosasaurs

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Ichthyosaurs

• The streamlined, rather porpoiselike ichthyosaurs
  
• varied from species measuring only 0.7 m long
• to 15-m-long giants
• Evolved from small animals

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Ichthyosaurs

• fully aquatic animals
• evolved from land-dwelling ancestors

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Ichthyosaurs evolved from reptiles
http//www.ucmp.berkeley.edu/people/motani/ichthyo
/intro.html
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Plesiosaurs

• The plesiosaurs,
• Mesozoic marine reptiles,
• belonged to one of two subgroups
• short necked and long-necked
• Most were modest sized animals 3.6 to 6 m long,
• one species found in Antarctica measures 15 m

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Plesiosaurs

• Although the plesiosaurs
• were aquatic animals,
• their fipperlike forelimbs
• probably allowed them to come out onto land

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Mosasaurs

• Mosasaurs were Late Cretaceous marine lizards
• related to the present-day
• Komodo dragon or monitor lizard
• Some species measured no more than 2.5 m long,
• but a few such as Tylosaurus were large,
• measuring up to 9 m
• Mosasaur limbs resemble paddles
• and were used mostly for maneuvering
• whereas the long tail provided propulsion

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Tylosaurus

• Tylosaurus was
• a large,
• Late Cretaceous
• mosasaur
• It measured up to 9 m long

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Mosasaur Skull

• Mosasaur skull on display
• in the Museum of Geology and Paleontology,
• University of Florence, Italy

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Mosasaurs Were Predators

• All mosasaurs were predators,
• and preserved stomach contents indicate
• that they ate fish, birds, smaller mosasaurs,
• and a variety of invertebrates
• including ammonoids

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And on land
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Land Plants

• Important changes took place
• in land plant communities
• flowering plants evolved during the Cretaceous
• soon became widespread and numerous
• The major groups of Paleozoic land plants
  persisted,
• but now they constitute less than 10 of all
  species

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Seedless Vascular Plants and Gymnosperms

• Seedless vascular plants and gymnosperms
• were prolific
• until angiosperms
• replaced many of them during the Mesozoic

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Angiosperms

• The long dominance of seedless plants and
  gymnosperms
• ended during the Early Cretaceous/Late Jurassic,
• many were replaced by angiosperms, or flowering
  plants
• Angiosperms probably evolved
• from specialized gymnosperms

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Fossil Angiosperms

• From the lower Cretaceous
• Potomac Group
• of the eastern United States

• Sapindopsis,
• Cecil County, Maryland

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The Diversification of Reptiles

• Reptile diversification began
• during the Mississippian Period
• with the evolution of the first animals to lay
  amniotic eggs
• From this basic stock of so-called stem reptiles
• all other reptiles, as well as birds and mammals,
  evolved

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Reptiles and Birds

• Relationships among fossil and living reptiles
  and birds

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First Dinosaurs

• Evolved from archosaurs (reptiles)
• Late Triassic
• Small, only 3 ft long
• Major characteristics
• Can walk fully upright - bipedal
• Special hip and ankle structure

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Archosaurs and the Origin of Dinosaurs

• Reptiles known as archosaurs
• archo meaning "ruling" and sauros meaning
  "lizard
• include crocodiles, pterosaurs (flying reptiles),
  dinosaurs, and the ancestors of birds
• Including such diverse animals
• in a single group implies
• that they share a common ancestor
• and indeed they possess several characteristics
  that unite them

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Dinosaurs Orders

• All dinosaurs possess
• a number of shared characteristics,
• yet differ enough for us to recognize two
  distinct orders
• the Saurischia
• and Ornithischia
• A distinctive pelvic structure characterizes each
  order
• 3 bones in pelvis illium, ischium, and pubis
• Saurischian pubis points down
• Orinischian pubis points back

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Distinctive Pelvic Structure

• Saurischian dinosaurs
• have a 1izardlike pelvis
• and are thus called lizard-hipped dinosaurs
• Ornithischians
• have a birdlike pelvis
• and are called bird-hipped dinosaurs
• Convergent evolution
• birdlike pelvic structure reinvented in
  Saurischian descendents (avian dinosaurs birds)

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Saurischians
www.enchantedlearning.com/subjects/dinosaurs/dinoc
lassification/Saurischian.html
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Saurischian Dinosaurs

• The saurischians,
• include two distinct groups
• known as theropods and sauropods
• All theropods
• were carnivorous bipeds
• ranging in size from tiny Compsognathus
• to giants such as Tyrannosaurus
• and similar species
• that might have weighed
• as much as 7 or 8 metric tons

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Dinosaur Cladogram