Transcript LECTURE 7: Mesozoic Era 248 mya – 65 mya

LECTURE 7: Mesozoic Era
248 mya – 65 mya
Periods of the Mesozoic Era
• Triassic
– 248 mya-206 mya
• Jurassic
– 206 mya-146 mya
• Cretaceous
– 146 mya-65 mya
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: today’s 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
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 sporebearing plants as drier environments replaced
swampy wetlands during the Mesozoic Era
Why did Plants Survive the
Permian Extinction?
• Plants are hardier than animals
• A simple lifestyle
– Plants’ basic needs—water, carbon dioxide, and a few
essential nutrients—are 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
• Part of a fern frond
Thaumatopteris brauniana
Triassic
• Ferns and other spore-bearing
plants were still part of the
landscape at the beginning of the
Mesozoic Era
But they were not as abundant,
diverse, or widespread as seedbearing plants, such as conifers
• Conifer branches with
leaves
Pagiophyllum
• 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
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)
• Cynodont synapsid
skull
Dadacon isaloi
• Dicynodont
synapsid
Lystrosaurus
a group of planteating synapsids
united by their sharp,
turtle-like beaks
What Existed in the Triassic Sea?
• Large Giant, Predatory
Reptiles
• Sauropterygian
– Augustasaurus hagdorni
Early 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
today’s sea turtles and penguins
do
What was the First Mammal?
• Megazostrodon and Morganucodon - 210 mya
– Hair
– “Toolkit” of different shaped teeth for different tasks
– Small (10-12 cm)
• Early Jurassic
Mammal
Morganucodon 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.
What are Archosaurs?
• Appear in the Triassic Period
• Diapsids
• Includes descendents, extinct, and living
species:
– Dinosaurs (including Birds)
– Crocodiles
– Pterosaurs
What were the First Dinosaurs?
• Eoraptor lunensis
– Small, Bipedal
– Carnivore
• Herrerasaurus
ischigualastensis
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 reptiles:all 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
• Pangaea pulls apart
Earth’s continents are
constantly—slowly—on
the move.
Pangaea assembled
completely during the
Triassic Period before
beginning to break
apart in the Jurassic
Period
Triassic Reptiles
Went Extinct at the End of the Triassic
• Phytosaur reptile
Machaeroprosopus
andersoni
With their long snouts
and sharp teeth,
phytosaurs looked, and
perhaps behaved, like
today’s crocodiles—
although they are not
closely related
• (Nostrils behind eyesCrocs nostrils on tip of
snout)
What New Predators Existed in
Jurassic Seas?
• Ichthyosaur reptile
Stenopterygius 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
What are Angiosperms?
• Flowering Plants- 140
mya
• Seeds enclosed in
Fruits
– Archaeanthus
linnenbergeri
– Greek angos, meaning
“vessel,” and sperma,
meaning “seed”
• Maple and legume
(angiosperm) leaves
Acer cretaceum
• Gleditsiophyllum aristatum
This 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
DINOSAUR DIVERSITY
• 2 Orders
– Saurischia (Lizard- Hipped)
• Theropods
– Bipedal carnivores/Bird Ancestors
• Sauropods
– Quadripedal herbivores (LARGEST
ANIMALS EVER)
– Ornithischia (Bird-Hipped)
• Mostly Quadrupedal Herbivores
Sauropods
• Brachiosaurus
• Argentinosaurus
(largest dinosaur)
Therapods
• First Dinosaurs
– Herrerasaurus and Eoraptor
• Tyrannasaurus rex
• Deinonychus
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
What was the First Bird?
• Archaeopteryx
– True Flyer
What happened at the End of the
Cretaceous?
• Mass Extinction #5
• Wiped out more
than 50% of life on
Earth—including all
dinosaurs except
birds
• Cause is debated
– Asteroid
– Volcanic Activity