LECTURE 7: Mesozoic Era 248 mya

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LECTURE 7 Mesozoic Era248 mya 65 mya
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Periods of the Mesozoic Era

• Triassic
• 248 mya-206 mya
• Jurassic
• 206 mya-146 mya
• Cretaceous
• 146 mya-65 mya

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What Significant Events Occurred During the
Mesozoic Era?(248 mya- 65 mya)

• Age of Dinosaurs
• Largest animals to have ever walked the earth
• Gave rise to birds todays only living dinosaurs
• Age of Reptiles
• Some started to fly, others went into the sea
• First crocodiles, snakes and turtles
• First Mammals
• First Birds
• First Angiosperms
• Flowering plants

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What Plants Survived the 3rd Mass Extinction?

• Less impact on plants than on animals
• Only around 20 of plant species died out
• Instead, the landscape continued to change
  gradually
• Hardy seed-bearing plants replaced spore-bearing
  plants as drier environments replaced swampy
  wetlands during the Mesozoic Era

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Why did Plants Survive the Permian Extinction?

• Plants are hardier than animals
• A simple lifestyle
• Plants basic needswater, carbon dioxide, and a
  few essential nutrientsare always present
• Built-in protection
• When confronted with environmental challenges,
  plants have their own protective gear. Seeds, for
  example, can lie dormant for long periods of time
  until conditions improve

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• Part of a fern frond Thaumatopteris
  braunianaTriassic
• Ferns and other spore-bearing plants were still
  part of the landscape at the beginning of the
  Mesozoic EraBut they were not as abundant,
  diverse, or widespread as seed-bearing plants,
  such as conifers

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• Conifer branches with leavesPagiophyllum
• Triassic Spore-bearing plants such as ferns need
  wet conditions for sperm to swim to the egg.But
  seed-bearing plants such as conifers can thrive
  in drier habitats because their sperm is
  transported inside a pollen grain

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What Animals Survived the Permian Extinction?

• Only one species out of five tetrapods survived
• Every tetrapod to have lived since, including
  you, can be traced back to these few survivors
• Synapsids, bounced back more quickly than
  reptiles or other tetrapods
• Mammals descended from these tetrapod survivors
• The most common synapsid fossils found from the
  beginning of the Triassic Period are
• Cynodonts
• Mammal-like teeth and may have had hair and
  whiskers
• Dicynodonts (most Common Triassic Synapsids)
• Non-mammalian 2 tusks (Testudines- turtles)

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• Cynodont synapsid skull Dadacon isaloi

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• Dicynodont synapsid Lystrosaurus a group of
  plant-eating synapsids united by their sharp,
  turtle-like beaks

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What Existed in the Triassic Sea?

• Large Giant, Predatory Reptiles
• Sauropterygian
• Augustasaurus hagdorniEarly sauropterygians had
  webbed hands and feet. Over millions of years,
  hands, feet, and limbs evolved into solid, broad
  paddles. Moving its paddles up and down as a
  bird moves its wings, sauropterygians would swim
  or fly through the water much like todays sea
  turtles and penguins do

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What was the First Mammal?

• Megazostrodon and Morganucodon - 210 mya
• Hair
• Toolkit of different shaped teeth for different
  tasks
• Small (10-12 cm)

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• Early Jurassic MammalMorganucodon oelheri
  With large eyes and a long snout, this little
  mammal may have been a nocturnal hunter with good
  vision and an acute sense of smell.

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What are Archosaurs?

• Appear in the Triassic Period
• Diapsids
• Includes descendents, extinct, and living
  species
• Dinosaurs (including Birds)
• Crocodiles
• Pterosaurs

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What were the First Dinosaurs?

• Eoraptor lunensis
• Small, Bipedal
• Carnivore
• Herrerasaurus ischigualastensis

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What Happened at the End of the Triassic 200 mya?

• Mass Extinction 4
• Caused By Continental Shift/Pangaea Starting to
  break apart
• On land, volcanic activity led to global warming
• many reptilesall large crurotarsans
  (non-dinosaurian archosaurs)
• many of the large amphibians were wiped out
• At sea, sea levels dropped, eliminating habitat
  for marine animals
• 50 of all marine life
• This event vacated ecological niches, allowing
  the dinosaurs to assume the dominant roles in the
  Jurassic period

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• Pangaea pulls apartEarths continents are
  constantlyslowlyon the move. Pangaea
  assembled completely during the Triassic Period
  before beginning to break apart in the Jurassic
  Period

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Triassic ReptilesWent Extinct at the End of the
Triassic

• Phytosaur reptile Machaeroprosopus
  andersoniWith their long snouts and sharp
  teeth, phytosaurs looked, and perhaps behaved,
  like todays crocodilesalthough they are not
  closely related
• (Nostrils behind eyes- Crocs nostrils on tip of
  snout)

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What New Predators Existed in Jurassic Seas?

• Ichthyosaur reptileStenopterygius quadriscissus
• One group of marine reptiles, the ichthyosaurs,
  changed dramatically as they evolved. They
  started off looking basically like reptiles with
  flippers. But over time they became much more
  dolphin-like, their form changing as their
  lifestyle changed

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What are Angiosperms?

• Flowering Plants- 140 mya
• Seeds enclosed in Fruits
• Archaeanthus linnenbergeri
• Greek angos, meaning vessel, and sperma,
  meaning seed

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• Maple and legume (angiosperm) leaves Acer
  cretaceum
• Gleditsiophyllum aristatumThis leaf on the top
  belonged to a maple tree. The one on the bottom
  belonged to a legume, a relative of pea and bean
  plants

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DINOSAUR DIVERSITY

• 2 Orders
• Saurischia (Lizard- Hipped)
• Theropods
• Bipedal carnivores/Bird Ancestors
• Sauropods
• Quadripedal herbivores (LARGEST ANIMALS EVER)
• Ornithischia (Bird-Hipped)
• Mostly Quadrupedal Herbivores

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Sauropods

• Brachiosaurus
• Argentinosaurus (largest dinosaur)

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Therapods

• First Dinosaurs
• Herrerasaurus and Eoraptor
• Tyrannasaurus rex
• Deinonychus

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Are Birds Dinosaurs?

• Yes!
• A group of theropod dinosaurs called dromaeosaurs
  (raptors)are among birds very closest relatives
• Dromaeosaur skeletons share many things in common
  with those of birds. Some are easier to see than
  others

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What was the First Bird?

• Archaeopteryx
• True Flyer

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What happened at the End of the Cretaceous?

• Mass Extinction 5
• Wiped out more than 50 of life on
  Earthincluding all dinosaurs except birds
• Cause is debated
• Asteroid
• Volcanic Activity