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Emma Schachner: The secret weapon that let dinosaurs take over the planet
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We've all heard the theories on why the dinosaurs died -- but how did they come to dominate the earth for so long in the first place? (Hint: it has nothing to do with their size, speed, spikes or fantastic feathers.) Travel back in time to 200 million years before their extinction with paleontologist Emma Schachner for a breath of fresh air on dinosaur history.
Emma Schachner - Comparative anatomist, paleontologist
Comparative anatomist and paleontologist Emma Schachner wants to know everything about the anatomy and evolution of reptiles and bird lungs: how they became so complex, why they have so many secondary functions and what role they played in their diversification and success. Full bio
Comparative anatomist and paleontologist Emma Schachner wants to know everything about the anatomy and evolution of reptiles and bird lungs: how they became so complex, why they have so many secondary functions and what role they played in their diversification and success. Full bio
Double-click the English transcript below to play the video.
00:13
We've all heard about
how the dinosaurs died.
how the dinosaurs died.
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The story I'm going to tell you
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happened over 200 million years
before the dinosaurs went extinct.
before the dinosaurs went extinct.
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This story starts at the very beginning,
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when dinosaurs were just
getting their start.
getting their start.
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One of the biggest mysteries
in evolutionary biology
in evolutionary biology
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is why dinosaurs were so successful.
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What led to their global dominance
for so many years?
for so many years?
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When people think about
why dinosaurs were so amazing,
why dinosaurs were so amazing,
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they usually think about the biggest
or the smallest dinosaur,
or the smallest dinosaur,
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or who was the fastest,
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or who had the most feathers,
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the most ridiculous armor,
spikes or teeth.
spikes or teeth.
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But perhaps the answer had to do
with their internal anatomy --
with their internal anatomy --
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a secret weapon, so to speak.
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My colleagues and I,
we think it was their lungs.
we think it was their lungs.
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I am both a paleontologist
and a comparative anatomist,
and a comparative anatomist,
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and I am interested in understanding
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how the specialized dinosaur lung
helped them take over the planet.
helped them take over the planet.
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So we are going to jump back
over 200 million years
over 200 million years
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to the Triassic period.
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The environment was extremely harsh,
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there were no flowering plants,
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so this means that there was no grass.
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So imagine a landscape
filled with all pine trees and ferns.
filled with all pine trees and ferns.
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At the same time,
there were small lizards,
there were small lizards,
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mammals, insects,
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and there were also carnivorous
and herbivorous reptiles --
and herbivorous reptiles --
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all competing for the same resources.
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Critical to this story
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is that oxygen levels have been estimated
to have been as low as 15 percent,
to have been as low as 15 percent,
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compared to today's 21 percent.
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So it would have been crucial
for dinosaurs to be able to breathe
for dinosaurs to be able to breathe
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in this low-oxygen environment,
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not only to survive
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but to thrive and to diversify.
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So, how do we know
what dinosaur lungs were even like,
what dinosaur lungs were even like,
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since all that remains of a dinosaur
generally is its fossilized skeleton?
generally is its fossilized skeleton?
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The method that we use is called
"extant phylogenetic bracketing."
"extant phylogenetic bracketing."
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This is a fancy way of saying
that we study the anatomy --
that we study the anatomy --
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specifically in this case,
the lungs and skeleton --
the lungs and skeleton --
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of the living descendants of dinosaurs
on the evolutionary tree.
on the evolutionary tree.
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So we would look at the anatomy of birds,
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who are the direct
descendants of dinosaurs,
descendants of dinosaurs,
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and we'd look at
the anatomy of crocodilians,
the anatomy of crocodilians,
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who are their closest living relatives,
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and then we would look at
the anatomy of lizards and turtles,
the anatomy of lizards and turtles,
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who we can think of like their cousins.
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And then we apply these anatomical data
to the fossil record,
to the fossil record,
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and then we can use that
to reconstruct the lungs of dinosaurs.
to reconstruct the lungs of dinosaurs.
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And in this specific instance,
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the skeleton of dinosaurs most closely
resembles that of modern birds.
resembles that of modern birds.
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So, because dinosaurs were competing with
early mammals during this time period,
early mammals during this time period,
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it's important to understand
the basic blueprint of the mammalian lung.
the basic blueprint of the mammalian lung.
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Also, to reintroduce you
to lungs in general,
to lungs in general,
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we will use my dog Mila of Troy,
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the face that launched a thousand treats,
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as our model.
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(Laughter)
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This story takes place
inside of a chest cavity.
inside of a chest cavity.
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So I want you to visualize
the ribcage of a dog.
the ribcage of a dog.
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Think about how
the spinal vertebral column
the spinal vertebral column
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is completely horizontal to the ground.
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This is how the spinal
vertebral column is going to be
vertebral column is going to be
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in all of the animals
that we'll be talking about,
that we'll be talking about,
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whether they walked on two legs
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or four legs.
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Now I want you to climb inside
of the imaginary ribcage and look up.
of the imaginary ribcage and look up.
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This is our thoracic ceiling.
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This is where the top surface of the lungs
comes into direct contact
comes into direct contact
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with the ribs and vertebrae.
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This interface is where
our story takes place.
our story takes place.
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Now I want you to visualize
the lungs of a dog.
the lungs of a dog.
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On the outside, it's like
a giant inflatable bag
a giant inflatable bag
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where all parts of the bag
expand during inhalation
expand during inhalation
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and contract during exhalation.
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Inside of the bag, there's a series
of branching tubes,
of branching tubes,
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and these tubes are called
the bronchial tree.
the bronchial tree.
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These tubes deliver the inhaled oxygen
to, ultimately, the alveolus.
to, ultimately, the alveolus.
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They cross over a thin membrane
into the bloodstream by diffusion.
into the bloodstream by diffusion.
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Now, this part is critical.
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The entire mammalian lung is mobile.
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That means it's moving
during the entire respiratory process,
during the entire respiratory process,
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so that thin membrane,
the blood-gas barrier,
the blood-gas barrier,
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cannot be too thin or it will break.
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Now, remember the blood-gas barrier,
because we will be returning to this.
because we will be returning to this.
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So, you're still with me?
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Because we're going to start birds
and it gets crazy,
and it gets crazy,
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so hold on to your butts.
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(Laughter)
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The bird is completely different
from the mammal.
from the mammal.
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And we are going to be
using birds as our model
using birds as our model
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to reconstruct the lungs of dinosaurs.
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So in the bird,
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air passes through the lung,
but the lung does not expand or contract.
but the lung does not expand or contract.
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The lung is immobilized,
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it has the texture of a dense sponge
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and it's inflexible and locked into place
on the top and sides by the ribcage
on the top and sides by the ribcage
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and on the bottom
by a horizontal membrane.
by a horizontal membrane.
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It is then unidirectionally ventilated
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by a series of flexible,
bag-like structures
bag-like structures
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that branch off of the bronchial tree,
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beyond the lung itself,
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and these are called air sacs.
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Now, this entire extremely delicate setup
is locked into place
is locked into place
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by a series of forked ribs
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all along the thoracic ceiling.
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Also, in many species of birds,
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extensions arise from the lung
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and the air sacs,
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they invade the skeletal tissues --
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usually the vertebrae,
sometimes the ribs --
sometimes the ribs --
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and they lock the respiratory
system into place.
system into place.
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And this is called
"vertebral pneumaticity."
"vertebral pneumaticity."
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The forked ribs and
the vertebral pneumaticity
the vertebral pneumaticity
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are two clues that we can hunt for
in the fossil record,
in the fossil record,
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because these two skeletal traits
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would indicate that regions
of the respiratory system of dinosaurs
of the respiratory system of dinosaurs
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are immobilized.
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This anchoring of the respiratory system
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facilitated the evolution
of the thinning of the blood-gas barrier,
of the thinning of the blood-gas barrier,
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that thin membrane over which oxygen
was diffusing into the bloodstream.
was diffusing into the bloodstream.
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The immobility permits this
because a thin barrier is a weak barrier,
because a thin barrier is a weak barrier,
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and the weak barrier would rupture
if it was actively being ventilated
if it was actively being ventilated
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like a mammalian lung.
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So why do we care about this?
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Why does this even matter?
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Oxygen more easily diffuses
across a thin membrane,
across a thin membrane,
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and a thin membrane is one way
of enhancing respiration
of enhancing respiration
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under low-oxygen conditions --
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low-oxygen conditions
like that of the Triassic period.
like that of the Triassic period.
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So, if dinosaurs did indeed
have this type of lung,
have this type of lung,
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they'd be better equipped to breathe
than all other animals,
than all other animals,
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including mammals.
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So do you remember the extant
phylogenetic bracket method
phylogenetic bracket method
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where we take the anatomy
of modern animals,
of modern animals,
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and we apply that to the fossil record?
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So, clue number one
was the forked ribs of modern birds.
was the forked ribs of modern birds.
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Well, we find that in pretty much
the majority of dinosaurs.
the majority of dinosaurs.
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So that means that the top surface
of the lungs of dinosaurs
of the lungs of dinosaurs
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would be locked into place,
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just like modern birds.
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Clue number two is vertebral pneumaticity.
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We find this in sauropod dinosaurs
and theropod dinosaurs,
and theropod dinosaurs,
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which is the group that contains
predatory dinosaurs
predatory dinosaurs
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and gave rise to modern birds.
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And while we don't find evidence
of fossilized lung tissue in dinosaurs,
of fossilized lung tissue in dinosaurs,
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vertebral pneumaticity gives us evidence
of what the lung was doing
of what the lung was doing
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during the life of these animals.
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Lung tissue or air sac tissue
was invading the vertebrae,
was invading the vertebrae,
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hollowing them out
just like a modern bird,
just like a modern bird,
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and locking regions
of the respiratory system into place,
of the respiratory system into place,
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immobilizing them.
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The forked ribs
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and the vertebral pneumaticity together
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were creating an immobilized,
rigid framework
rigid framework
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that locked the respiratory
system into place
system into place
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that permitted the evolution of that
superthin, superdelicate blood-gas barrier
superthin, superdelicate blood-gas barrier
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that we see today in modern birds.
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Evidence of this straightjacketed
lung in dinosaurs
lung in dinosaurs
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means that they had
the capability to evolve a lung
the capability to evolve a lung
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that would have been able to breathe
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under the hypoxic, or low-oxygen,
atmosphere of the Triassic period.
atmosphere of the Triassic period.
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This rigid skeletal setup in dinosaurs
would have given them
would have given them
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a significant adaptive advantage
over other animals, particularly mammals,
over other animals, particularly mammals,
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whose flexible lung couldn't have adapted
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to the hypoxic, or low-oxygen,
atmosphere of the Triassic.
atmosphere of the Triassic.
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This anatomy may have been
the secret weapon of dinosaurs
the secret weapon of dinosaurs
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that gave them that advantage
over other animals.
over other animals.
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And this gives us an excellent launchpad
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to start testing the hypotheses
of dinosaurian diversification.
of dinosaurian diversification.
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This is the story of
the dinosaurs' beginning,
the dinosaurs' beginning,
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and it's just the beginning of the story
of our research into this subject.
of our research into this subject.
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Thank you.
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(Applause)
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ABOUT THE SPEAKER
Emma Schachner - Comparative anatomist, paleontologistComparative anatomist and paleontologist Emma Schachner wants to know everything about the anatomy and evolution of reptiles and bird lungs: how they became so complex, why they have so many secondary functions and what role they played in their diversification and success.
Why you should listen
As an anatomy professor at LSU Health Sciences Center in New Orleans, Emma Schachner's research uses an interdisciplinary approach to study the soft tissue and skeletal anatomy of a broad range of animals including alligators, chameleons, parrots and ostriches. She uses these data to reconstruct the biology of extinct reptiles, particularly dinosaurs and the fossil ancestors of crocodilians. She also specializes in the 3D digital modeling of anatomy from CT and MR images as well as scientific illustration, which merges anatomy, art and scientific communication.
Schachner lives in New Orleans with her two rescued pit bull mixes and insta-famous canine overlords: Mila of Troy and Augustus of the Velvet Legions.
Emma Schachner | Speaker | TED.com