Transcript Mesozoic Era 2014bx

The Age of Dinosaurs
Setting the Stage
 The Mesozoic Era is the Age of the Dinosaurs and lasted
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almost 180 million years from approximately 250 to 65 mya.
This era includes 3 well known periods called the Triassic,
Jurassic, and Cretaceous periods.
A mass-extinction marked the beginning and end of the
Mesozoic Era. The event that caused the transition from the
Paleozoic era to the Mesozoic era, The Permian Extinction
was the greatest extinction this earth has seen. This
extinction wiped out about 95% of all marine life and 70%
of land-life.
This allowed the dinosaurs to diversify and enter niches left
unoccupied by the Permian Extinction.
The era ended with "The Great Extinction" which marked
the end of the dinosaurs as the Cenozoic era began.
Arrangement of Continents
 At the beginning of the Mesozoic, all of the world's
continents were combined into the supercontinent of
Pangaea, which rifted into Laurasia in the north and
Gondwanaland in the south. By the end of the era most
of continents had separated into their present form.
Estimated Global Temperatures in
the Proterozoic Eon
Triassic
• Time – 251 - 199 million years ago
(Mesozoic Era)
 During the Triassic, the Earth's land mass was a single
supercontinent called Pangaea ("all the land"). Pangaea
was surrounded by the world-ocean known as
Panthalassa ("all the sea").
 The global climate during the Triassic was mostly hot and
dry, with deserts spanning much of Pangaea's interior.
However, the climate shifted and became more humid as
Pangaea began to drift apart.
 The Earth's biosphere impoverished; it would take well
into the middle of the period for life to recover its former
diversity. Therapsids and archosaurs (reptiles) were the
chief terrestrial vertebrates during this time.
Triassic Biology
 The oceans teemed with the coiled-
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shelled ammonites, mollusks, and
sea urchins that survived the
Permian extinction and were quickly
diversifying.
The first corals appeared, though
other reef-building organisms were
already present.
Giant reptiles such as the dolphinshaped ichthyosaurs and plesiosaurs
preyed on fish and ancient squid.
Pterosaurs, a group of flying reptiles,
took to the air.
On firm ground, moss, liverwort,
and ferns carpeted forests of
conifers, ginkgoes, and palm-like
cycads.
Triassic Biology - The First Mammals
 But perhaps the biggest changes
came with the evolution of
dinosaurs and the first mammals in
the late Triassic, starting around
230 million years ago.
 One of the earliest true mammals
was the three-foot-long (onemeter-long) Eozostrodon. The
shrew-like creature laid eggs but
fed its young mother's milk - a
monotreme like today’s echidna or
platypus.
 While dinosaurs dominated many
ecological niches, mammals
remained small.
Therapsids - reptiles that
had developed some
mammalian characteristics
Triassic Biology - The First Dinosaurs
 Among the first dinosaurs was
the two-footed carnivore
Coelophysis, which grew up to 9
feet (2.7 meters) tall, weighed
up to a hundred pounds (45
kilograms), and probably fed on
small reptiles and amphibians.
 It showed up about 225 million
years ago. A few million years
later came the 27.5-foot-long (8meter-long) herbivore called
Plateosaurus.
Triassic Geology
 During the Triassic,
almost all of the Earth's
land mass was combined
into a single
supercontinent called
Pangaea (“All the Land”)
which straddled the
equator
 From the east a vast gulf
entered Pangaea, the
Tethys sea.
Mean atmospheric ca. 16 Vol %
O2 content over
(80 % of modern
period duration
level)
Mean atmospheric ca. 1750 ppm
CO2 content over (6 times preperiod duration
industrial level)
Mean surface
temperature over
period duration
ca. 17 °C
(3 °C above
modern level)
The End of the Triassic
 This period ended with another mass extinction, followed
by volcanic eruptions about 208-213 million y.a.
 The suspected cause is global warming related to the increase in
volcanism.
 During this extinction, Pangaea began to break apart. As a result of the
extinction, 35% of all families died out.
 Dinosaurs, however, survived and went on to dominate the Jurassic.
Jurassic
• Time – 199 - 145 m.y.a
(Mesozoic Era)
 The Jurassic is named from the
Jura Mountains of the Alps.
 The Jurassic constitutes the
middle period of the Mesozoic
Era.
 The start of the period is
marked by the major Triassic–
Jurassic extinction event. Two
other small extinction events
occurred during the period
Jurassic Geology
 During the early Jurassic
period, the supercontinent
Pangaea broke up into the
northern supercontinent
Laurasia and the southern
supercontinent Gondwana
 The Gulf of Mexico opened in
the new rift between North
America and what is now
Mexico's Yucatan Peninsula.
 The Jurassic North Atlantic
Ocean was relatively narrow,
while the South Atlantic did
not open until the following
Cretaceous period, when
Gondwana itself rifted apart.
Jurassic Geology
 By subduction of the oceanic
plates, mountains began to
form along the west coast of
North America. Throughout
the Middle to Late Triassic,
mountains continued to form
along the coast extending
from Alaska to Chile.
 The Tethys Sea closed, and the
Neotethys basin appeared.
Climates were warm, with no
evidence of glaciation.
 As in the Triassic, there was
apparently no land near either
pole, and no extensive ice caps
existed.
Jurassic Biology
 On land, the Triassic reptiles to
one dominated by dinosaurs
alone. The first birds also
appeared during the Jurassic,
having evolved from a branch of
suarischian theropod dinosaurs.
 Other major events include the
appearance of the earliest
lizards, and the evolution of
therian mammals, including
primitive placentals.
 Gymnosperms (plants with
cones (Conifers)) appear.
Dinosaur Evolution
 Dinosaurs evolved along two
lines - the Ornithiscian or
bird-hipped dinosaurs and the
Saurischian or lizard hipped
dinosaurs.
 Predators such as
Velociraptors and T. Rex , and
massive dinosaurs such as
Brachiosaurs were
Saurischians.
 Dinosaurs such as Triceratops,
Stegasaurus and horn-billed
dinosaurs were examples of
Ornithischians
 Ironically, birds evolved from
Saurischians.
Jurassic Geology
 By the beginning of the
Jurassic, Pangaea had
begun rifting into two
landmasses, Laurasia to
the north and
Gondwana to the south.
 This created more
coastlines and shifted
the continental climate
from dry to humid, and
many of the arid deserts
of the Triassic were
replaced by lush
rainforests.
Mean atmospheric ca. 26 Vol %
O2 content over
(130 % of modern
period duration
level)
Mean atmospheric ca. 1950 ppm
CO2 content over (7 times preperiod duration
industrial level)
Mean surface
temperature over
period duration
ca. 16.5 °C
(3 °C above
modern level)
Two Dinosaur Cladograms
Cretaceous
• Time – 145 - 65 million years ago
(Mesozoic Era)
 The Cretaceous derived from the Latin "creta" (chalk),
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usually abbreviated K for its German translation Kreide
(chalk).
The Cretaceous is followed by the Cenozoic era. It is the last
period of the Mesozoic Era, and, spanning 79 million years,
the longest period of the Phanerozoic Eon.
The Cretaceous was a period with a relatively warm climate,
resulting in high sea levels and creating numerous shallow
inland seas.
This era was warm and moist with excellent conditions for
abundant life on land almost from pole to pole.
Extremely warm oceans may have lead to anoxic conditions in
deep water. (very low O2 levels toxic to marine life)
Cretaceous Biology
 The oceans and shallow inland seas
were populated with now-extinct
marine reptiles, ammonites and
rudists, while dinosaurs
continued to dominate on land.
 At the same time, new groups of
mammals and birds, as well as
flowering plants, appeared.
 Flowering plants (angiosperms)
spread during this period, although
they did not become predominant
until late in the Cretaceous. The first
representatives of many leafy trees
appeared in the Cretaceous.
Cretaceous Biology
 The evolution of plants was aided by
the appearance of bees; in fact
angiosperms and insects are a good
example of coevolution.
 High oxygen levels produced giant
insects. However these may have
gone extinct with the appearance of
birds.
 On land, mammals were a small and
still relatively minor component of
the fauna. Early marsupial mammals
evolved in the Early Cretaceous,
with true placentals emerging in the
Late Cretaceous period.
An actual Velociraptor - much
smaller, feathered compared
to the movie version
Cretaceous Dinosaurs
 Dinosaurs continue to diversify. Birds evolve from the
small therapod predators that we know as “raptors”.
 These dinosaurs develop feathers (probably for insulation
and display) and gradually develop into gliders then fliers.
 The Tyrannasaurus Rex appears in the late Cretaceous and
exists until the K-T extinction event.
Cretaceous Geology
 During the Cretaceous, the
former supercontinent of
Pangaea completed its tectonic
breakup into present day
continents, although their
positions were substantially
different at the time.
 The Atlantic Ocean widened.
 Though Gondwana was still
intact in the beginning of the
Cretaceous, it broke up into
South America, Antarctica and
Australia rifted away from Africa
(though India and Madagascar
remained attached to each
other)
Cretaceous Geology
 Thus, the South Atlantic and
Indian Oceans were newly
formed. Such active rifting lifted
great undersea mountain chains
along the welts, raising sea levels
worldwide.
 To the north of Africa the Tethys
Sea continued to narrow. Broad
shallow seas advanced across
central North America (the
Western Interior Seaway) and
Europe, then receded late in the
period, leaving thick marine
deposits sandwiched between
coal beds.
 At the peak of the Cretaceous,
one-third of Earth's present land
area was submerged.
Cretaceous Geology
 During the Cretaceous
Gondwana breaks into
South America,
Antarctica, and
Australia, Africa, India
and Madagascar.
 Laurasia breaks into
North America, Europe
and Asia.
 The map of the Late
Cretaceous shows most
of today’s continents.
Mean atmospheric
O2 content over
period duration
ca. 30 Vol %
(150 % of modern
level)
Mean atmospheric
CO2 content over
period duration
ca. 1700 ppm
(6 times preindustrial level)
Mean surface
temperature over
period duration
ca. 18 °C (4 °C above
modern level)
The Cretaceous Extinction
 The K-T (Cretaceous -
Tertiary) extinction event is
widely known as it marked
the end of dinosaurs.
 Two major geological
upheavals occurred at this
time approximately 65
million years ago - the
volcanic event known as the
Deccan Traps flood basalts
and the Chicxulub meteorite
which struck the Yucatan
Peninsula in Mexico.
Deccan Traps
 The Deccan Traps formed between
60 and 68 million years ago, at the
end of the Cretaceous period.
 The major part of this event occurs
at the K-T boundary.
 This series of eruptions may have
lasted less than 30,000 years in
total. The original area covered by
the lava flows is estimated to have
been as large as 1.5 million km²,
approximately half the size of
modern India.
 These layered basalts are over a mile
deep in places. The eroded
sediment from this rock is
responsible for fertile soils.
Deccan Traps
 The Deccan Traps are an
example of an LIP (Large
Igneous Province) where
basalts have flooded over
continental land masses.
 There are several throughout
the world (including the
Siberian traps and the
Columbia Flood Basalts of the
western USA)
 These events are thought to
release large amounts of CO2
and atmospheric pollutants
which could drastically change
climate.
Evidence of the K-T
extinction event
 The Cretaceous-Tertiary extinction
event, or the K-T event, is the name
given to the die-off of the dinosaurs
and other species that took place
some 65.5 mya.
 For many years, paleontologists
believed this event was caused by
climate and geological changes that
interrupted the dinosaurs’ food
supply.
 However, in the 1980s, father-andson scientists Luis (1911-88) and
Walter Alvarez (1940-) discovered in
a distinct layer of iridium–an
Walter and Luis Alvarez standing at
element found in abundance only in the Gubbio Clay layer, the K-T
space–that corresponds to the
boundary rich in Ir and microtektites.
precise time the dinosaurs died.
Chicxulub Crater
 This suggests that a comet,
asteroid or meteor impact
event may have caused the
extinction of the dinosaurs.
 In the late 1980’s, petroleum
geologists working for PEMEX
located an arc shaped
gravitational anomaly in the
Gulf of Mexico.
 What they had found was the
massive Chicxulub Crater at
the tip of Mexico’s Yucatán
Peninsula, which dates to the
K-T boundary.
Chicxulub Crater
 The crater is not visible at
the Earth’s surface as it is
buried in 65 million years of
new marine sediments.
 Seismic and gravitational
anomaly images taken in
the 1990’s give a clear
picture of the location of
the crater.
 Additionally, it turns out
that limestone sinkholes
called cenotes perfectly
line the edge of the crater.
Artist’s rendering of the crater
after it was formed
Alternate Theories
 Besides dinosaurs, many other species of mammals, amphibians
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and plants died out at the same time. Over the years,
paleontologists have proposed several theories for this extensive
die-off.
One early theory was that small mammals ate dinosaur eggs,
thereby reducing the dinosaur population until it became
unsustainable.
Another theory was that dinosaurs’ bodies became too big to be
operated by their small brains.
Some scientists believed a great plague decimated the dinosaur
population and then spread to the animals that feasted on their
carcasses.
Starvation was another possibility: Large dinosaurs required vast
amounts of food and could have stripped bare all the vegetation in
their habitat.
But many of these theories are easily dismissed. If dinosaurs’ brains
were too small to be adaptive, they would not have flourished for
160 million years. Also, plants do not have brains nor do they suffer
from the same diseases as animals, so their simultaneous extinction
makes these theories less plausible.
K-T Extinction Videos
 http://www.history.com/topics/why-did-the-dinosaurs-die-out
 History Channel
 http://www.youtube.com/watch?v=ubBebEywNmE (KT
Asteroid & Dinosaurs Extinction) (7:05)
 http://www.youtube.com/watch?v=_COcHHvte-0 (2:25)
(meteorite strike)
 http://www.youtube.com/watch?v=Dcp0JhwNgmE (Chicxulub
Tsunami (4:05))
 http://www.youtube.com/watch?v=4WwJL25xVG8 (K-T
extinction event - 44:44)
 http://www.youtube.com/watch?v=uTvFzm3jRCU (The
Siberian Traps and the Volcanic Mass Extinction Theory
(Full Documentary) - Permian extinction)