The Mesozoic Era
When Dinosaurs Ruled the Earth
The Mesozoic Era
 Began approximately 245 million years ago
after a major mass extinction.
 Is subdivided into 3 periods:
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Triassic
Jurassic
Cretaceous
 Ends about 66 million years ago with a
major mass extinction
Mesozoic Reptiles
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Turtles
Crocodiles/Alligators
Lizards
Ichthyosaurs (large marine reptiles)
Pterosaurs (large flying reptiles)
Dinosaurs (land dinosaurs)
Dinosaurs Myths
 All dinosaurs are the same
 Everything that is big and extinct is a
dinosaur
 All dinosaurs lived at the same time
 All ‘dinosaurs’ are extinct…
...you’ll see!
The Triassic Period
245 - 206 million years ago
 Immediately after the Permian Mass
Extinction
 Lots of new area is open for animals to live
 Three general types of animals:
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holdovers from before the extinction
new groups that lasted only a short time
new groups that lasted a long time
The Triassic World
Triassic Plant Life
 Mosses
 Scale Trees (like palm trees)
 Ginkos (my favorite)
Two Groups of Dinosaurs
 Ornithischian
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Hips were similar to modern bird hips
Carnivorous short-necked
Herbivorous, long-necked
 Saurischian
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Hips were similar to reptile hips
Herbivorous with grinding-teeth
Herbivorous without grinding-teeth
Earliest Dinosaurs
(Triassic)
Pisanosaurus
Length:3 feet
Height:1 foot
Weight:15 pounds
Eoraptor:
Length:3 feet
Height:1 feet
Weight:20 pounds
Lesothsaurus:
Length:3 feet
Height:1 foot
Weight:15 pounds
The Jurassic Period
206 - 144 Million Years Ago
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Giant plant-eating dinosaurs
Vicious carnivore dinosaurs
Oceans full of fish, squid, sharks, etc.
Ichthyosaurs and Plesiosaurs
Pterosaurs
Birds
The Jurassic World
Jurassic Plant Eating Dinosaurs
 Many different forms
 Many had ‘armor’ to
protect themselves
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Triceratops
Triceratops
Ankylosaurus
 Many very large
(larger than a
Rhino/Hippo)
 Some were extremely
large (as long as a city
block): Diplodocus
Ankyloasaurus
Diplodocus
Jurassic Carnivorous Dinosaurs
 Many different forms
 Some were very large:
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Tyrannosaurus Rex
Allasaurus
 Some were smaller:
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Raptors, and many
more
 All had sharp teeth,
claws, and speed
Jurassic Marine Dinosaurs
 Most with similar
shapes as a dolphins
or sharks
 Ate fish and other
marine animals
 Some were VERY
large
 All could swim VERY
fast
Ichthyosaurus
Jurassic Pterosaurs
 Pterodactyls and
Pterosaurs
 Most had trouble
‘walking’
 Were very good flyers
 Had hollow bones
 Small (~ 1 foot) and
very large (~ 16 feet)
More Pterodactyls
Jurassic Birds(?) - Archaeopteryx
 Not a Pterosaur
 Jaws and bone structure like
dinosaurs
 Bones are hollow, like birds
 Feathers
 Was this an evolutionary
link between dinosaurs and
birds?
The Cretaceous Period
144 - 66 million years ago
 The last period when Dinosaurs lived
 Ends with a mass extinction around 66
million years ago
 First flowering plants!
The Cretaceous World
Cretaceous Plants
 First plants with
flowers
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Their appearance was
very rapid
They appeared at the
same time as the
number of insects
increased…
 Could insects have
helped the flowering
plants evolve?
The Cretaceous Mass Extinction
 Approximately 60% of all species went
extinct.
 Affected many land animals/plants
 Affected fewer marine animals
What organisms went extinct?
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All dinosaurs
All pterosaurs
All ichthyosaurs
Many terrestrial plants
Many marine animals
What organisms survived?
 MAMMALS (!)
 Birds
 Many plants (ferns were the most successful
plant for a while)
 Trees with flowers
 Small lizards/crocodiles/alligators/turtles
 Fish, squids, sharks, etc.
What caused the extinction?
 Meteorite impact theory
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66 million years ago, a ~10 km wide meteorite
struck the Earth near what is now Mexico.
Meteorite Impact
 This is an EXAGGERATED view of a meteorite
impact
How could a meteorite impact
cause a mass extinction?
 The impact caused shock waves, tidal waves, and
sent a tremendous amount of dust into the
atmosphere
 As the dust re-entered the Earth’s atmosphere, it
would have instantly heated the atmosphere
causing tremendous forest fires
 The dust could have caused the Earth’s climate to
cool in the long-run by blocking sunlight
 Plants, animals, etc went extinct due to the climate
changes and competition between organisms
Meteorite Impact Evidence #1
 Unique Quartz Crystals
 Very commonly formed under high
pressure/temperature
 This quarts was only found in meteorite
craters and nuclear testing sites
Meteorite Impact Evidence #2
 Iridium
 An element that is very rare in Earth
rocks and very common in meteorites
 The layer of rocks above the last dinosaur
bones contains ~160 times ‘normal’
levels of iridium
Problems with the Meteorite
Impact Hypothesis
 Why were some animals affected, while
others were not?
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Why did birds survive, and dinosaurs (a very
close relative) not?
Why did small reptiles survive when small
dinosaurs didn’t?
Why did mammals survive?
Out-dated Hypotheses
 Hay Fever - caused by flowering plants
 Dinosaurs were so big, that they crushed
themselves
 Mammals out-competed the dinosaurs
 Mammals ate all the dinosaur eggs
 Cosmic rays killed the dinosaurs