>>MARK NORELL: When I started
my job here 23, 24 years ago,
at that point, I had never
worked on dinosaurs before,
believe it or not.
I've worked on fossil
lizards and a lot
of other kind of
stuff, but they said
if you want a job
here, if we hire you,
you have to work on dinosaurs.
And I said sure, I can figure
this out, and we'll be fine.
But there were a lot of
people who thought that birds
might be related to crocodiles.
They might be related to
ancestral archosaurs, which
is just a weird
group of reptiles,
but they might be related
to birds, as well.
And the ideas had
just been proposed
that birds were nested
within dinosaurs-- that birds
are a kind of dinosaur,
just like humans
are a kind of primate.
That's over.
We all know now that birds
are more closely related
to Tyrannosaurus rex
than Tyrannosaurus rex is
to almost any other dinosaur
that you may have heard of.
But now we're really getting
into the interesting parts
of how that we can
understand some of the things
about how these animals
acted and behaved in the past
by using living
analogs to do that.
And the focus of a lot of
the work that we're doing now
is the neurobiology
of these animals.
And Amy has been the
prime mover and shaker
in my extended laboratory
about this stuff
over the last few
years using all sorts
of different new technologies to
be able to reconstruct dinosaur
brains.
And now we're moving toward what
some of those reconstructions
may mean as far as behaviorally
and physiologically.
So with that, we'll get going.
So Amy.
>>AMY BALANOFF: All right.
Well, thanks Mark.
Yeah.
This is great to
be up here tonight.
This is very exciting, to
talk about a little bit
of my research.
So the first question
might be well,
why would you want
to study bird brains?
For one, birds are one of
the few groups of vertebrates
that attain powered flight.
So that's one reason why
we're interested in what's
going on in the evolution
of the bird brain.
The other reason
is that birds reach
some of the largest
endocranial volumes
within vertebrate evolution.
So they have volumes
on par with mammals.
And so this is a great system
to study within invertebrates.
We can study the origin
of the bird's brains
by looking only at living taxa.
Right here, I've highlighted
birds and crocodilians.
Birds and crocodilians
are most closely related
to each other among
living vertebrates.
But if you look
only at these taxa,
then you're missing an
incredible amount of evolution.
The division between
these two groups
occurred almost 220
million years ago.
So there's all of these
non-avian dinosaurs
plus pterosaurs
that are going to be
absent from your analyses.
And this is what Mark and I are
interested in looking at what's
going on in this, what we call
a Sim lineage or these extinct
taxa, to see how their
brains are changing.
>>NORELL: Yeah.
So one of the things that we
really want to look at in this
is that if you look
fundamentally at a bird brain,
and we'll get a little more
into this a little bit later,
it's very like a
mammalian brain.
Anybody who's ever seen the
inside of a human skull,
or had a CAT scan, or whatever
knows that the brain totally
fills the whole
volume of the skull.
In crocodiles, it doesn't.
There's a lot of
loose space in there.
They're like a lizard
in everything else.
So there's been this
total advancement
in size of the brain
relative to the body,
and elaboration of
the brain, as well.
And parallely, that
happens in mammals.
If you look at the most
primitive mammals or mammal
line lineages, that it's
known that they basically
have something that looks
like a crocodile brain.
But when you get
to a modern mammal,
it has something that
looks like a bird brain.
So if it just happens
once, it's a one-off.
But if it happens twice, that
there must be a reason for it.
>>BALANOFF: Yeah.
I'd say the underlying
developmental networks
and gene expressions, what
Mark was talking about
is one of the things that we're
really interested in getting
at in the future.
But as for now, what
I want to talk about
is to look at some of
these birdlike characters
as the fossil record
really is basically
becoming more complete.
In the last 20 years, there
have been incredible discoveries
in Mongolia.
Mark and Dr. Mike Novacek as
well have been able to find--
>>NORELL: And yourself.
[LAUGHING]
>>BALANOFF: --I
have been out there.
But as they find these
incredibly complete,
beautifully articulated
fossils out in the Gobi Desert.
And also again, Mark's found
these incredible specimens
in China.
We're finding that those
characters that we initially
thought were just associated
with living birds, things
like feathers and a
furcula, or a wishbone,
or even behaviors like nesting
clutches of eggs-- things
that we first thought were
associated only with living
birds-- well, it turns out that
if you look at that diversity
that I showed you before
of non-avian dinosaurs,
it turns out that these
characters actually
evolved much earlier in
the evolutionary history
of that avian lineage
than we thought before.
And so again, it's
something that if you
want to study the origins
of the avian brain.
Well, then it's
really not surprising
that you wouldn't want to go
earlier into their history
and not just look
at living taxa,
but look at some of these
non-avian dinosaurs, as well.
>>NORELL: Some of it is just
that if you think that there is
a dichotomy between birds and
dinosaurs, there really isn't.
Because probably,
the iconic dinosaur
that you can walk two
galleries away and go see
is Tyrannosaurus rex.
And Tyrannosaurus
rex had feathers.
Tyrannosaurus rex
had a wishbone.
Tyrannosaurus rex
had hollow bones.
Tyrannosaurus rex probably sat
on top of its nests of eggs,
just like modern birds do--
so that these are not really,
really different animals.
Most non-avian dinosaurs
were not big lizards.
They're more like weird birds
than they are like big lizards.
So we have to get by
that first, and then we
can start thinking about them
in a totally different way.
>>BALANOFF: Yeah.
I'd say it's becoming
a little less
clear what we think a bird is.
It's not exactly-- like I
said, all those characters
that you thought were bird-like
characters are evolving
much earlier in their history.
To look at the avian brain,
we use CT data, very much
like any kind of CT scan that
you'd have in the hospital--
god forbid-- if you have a
head injury or something.
So that same kind of technology,
we use to study fossils.
It's not really a new thing.
We've used this to study fossils
probably for the past 20 years
or so.
Typically, the way we
use it is to either just
look at the internal
anatomy of say, a dinosaur
skull, or a mammal skull,
or anything like that.
We've also used it to separate
the matrix of a fossil
from the bone.
And so a lot of
things that wouldn't
be visible in just
the specimen itself
are made easily visible
with the use of CT
data and this digital data.
Another example is a
project that Mark and I
both worked on this
Cretaceous dinosaur egg.
So we CT scanned it and
then basically isolated
all of the embryonic
bones within the egg,
and rendered them
separately so that we
could describe each bone.
And it helped us identify what
was going on within that egg.
So this is the
technology that we're
using to look at these brains
as dinosaur brains as well.
So here's just an example
of how we do this.
So Mark mentioned
in birds, birds fill
most of the cranial cavity.
And in taxa that fill the
cranial cavity, things
like birds and mammals--
so things with very
large, large brains--
in these taxa, as
the brain develops,
it leaves an impression on the
internal surface of the brain
case so that if you
can somehow digitally
fill in that space, that
cranial cavity space,
and then digitally
remove the bones--
well, then you'll have what is
basically a cast of the brain.
And this gives you the
external surface of the brain.
There's really no way to get at
the internal or deep structures
of the brain at this time.
But we can at least look at
that sort of official morphology
of the avian brain.
This right here is
a living albatross.
And this is what we
call an endocast.
This is an endocast
of a living albatross.
>>NORELL: What's so nice
about this technique
is that what we know about
the brain morphology of living
birds is basically
the same thing,
but done in a much
more primitive way
because 30 years
ago, people wanted
to look at the brain
of a living bird
that before these
techniques were developed,
they would make
a skeleton of it.
Then they would blow latex
on the inside of the skull
and then dissolve
the skull around it.
You would just have
a physical thing
instead of a virtual
thing, like we have now.
But they're directly comparable.
>>BALANOFF: It's
directly comparable.
And it's so much
nicer, because it's
not disruptive to
the specimen at all.
>>NORELL: It doesn't
smell bad either.
>>BALANOFF: It
doesn't smell bad.
There are other examples
where people would serially
section the skull and
then manually fill
in that cranial cavity space.
And that's how they would
create their endocast.
So basically, they
just stack it back up,
which is the same thing
that we're doing here,
except that we're
doing it digitally.
So it's non-disruptive to the
specimens, which is really key.
So this, what you see
spinning on the screen here
is an Oviraptor dinosaur that
Mark collected in the field.
This is the endocast,
and this is actually
an endocast of the bony
labyrinth of the ear, as well.
So this is an example of what
we can do with this technology.
We're not the first
ones to really look
at these kinds of analyses.
This is an example
from Larson et al.
Basically, the circle
represents the distribution
of brain volumes versus
body size of living birds.
Birds have a relatively
large brain volume
compared to other reptiles.
So this is like lizards,
and snakes, and turtles,
and things like that.
What you want to notice is
that right in the middle
is Archaeopteryx,
which has basically
been considered the first
bird, because it lies
close to the origin
of powered flight
and probably high
powered flight itself.
>>NORELL: Maybe.
>>BALANOFF: Maybe.
It's a possibility.
That's not my area of expertise.
So Archaeopteryx has been set
up as this transitional fossil
between quote, reptiles
and crown group birds,
or living birds.
They are able to draw
from basal Coelurosaurs.
So these are things
like Tyrannosaurus.
They also, of course, included
Archaeopteryx in their studies,
as well as living birds.
But given that sampling, it's
not really that surprising
that Archaeopteryx is going
to fall right in the middle
in that distribution.
So it's not surprising
that it's going
to have that kind of
intermediate position.
>>NORELL: So one of
the things that we've
been able to really bring to the
table is both these ideas that
have been floating around
there for a long time combined
with some great machinery exist
both at University of Texas
Austin, and here, at the
American Museum to be
able to scan these things.
But the most important thing
is that the real currency
in understanding these things
is the fossils themselves.
So about half of
these things are
things that we've excavated
in Mongolia over the last two
decades.
>>BALANOFF: Exactly.
And those are what we were
able to bring to this analysis.
So those previous studies--
like I said, they are very
limited in their sampling.
What we were able to do is
add many of these fossils
that we've been able to
collect in the Gobi Desert,
a few from China, as well.
Those specimens that
we've been able to add
have been very close are much
closer to the origin of living
birds than those previous
analyses were able to sample
from.
So that's really one thing
that sets our analysis apart
from those others.
Here are our results.
This is a plot of total
endocranial volume
versus body size.
>>NORELL: How big your
brain is, compared
to how big your body is.
>>BALANOFF: Yeah.
Exactly.
Thank you.
So in blue, what we're
showing is the distribution
of living birds.
And compared to all these
other non-avian dinosaurs,
they really have a
very large brain.
But what's really different
about our analysis
is that Archaeopteryx
no longer lies
in that intermediate position.
But all those other colored
dots on the screen, those
are all other
non-avian dinosaurs
that are closely related
to Archaeopteryx.
Not Archaeopteryx.
They're a little bit further
away from the origin of birds
as well.
And what this shows is
that Archaeopteryx doesn't
really especially have--
there is nothing especially
special about its brain volume.
But basically, it has
a volume that you would
expect of a non-avian dinosaur.
Now, one other thing that we
were able to do with these data
was to partition the brain.
So we were able to isolate
different parts of the brain.
So we could look at
the olfactory tracks
or that part of the brain
that's responsible for smell--
the cerebrum, the
major part of the brain
that's in charge of any
kind of cognitive functions.
The optic lobes obviously--
vision, and the cerebellum,
and brain stem, as well.
So we were able to
partition this brain up,
which is something that
no one else has really
thought about doing before.
We can look at each of
these regions with respect
to the total endocranial volume.
And just as an example,
what I'm showing
you here is the volume
of the olfactory bulbs
with respect to the
total endocranial volume.
So is this how big the
olfactory bulbs are with respect
to the rest of the brain.
Birds have a very
poor sense of smell.
>>NORELL: You can
really think of it
is that you look at mammals.
And mammals are
pretty dull colored.
And one of the reasons
that they're dulled colored
is because mammals
don't see in color.
There's very few mammals.
Only basically
primates see in color.
All that stuff you've heard
about red capes and balls--
it's not true.
They see in black and white.
Not only do birds see in color,
they see in far more color
than we do.
They see way out
into the infrared.
I mean not the infrared,
the ultraviolet, rather.
A lot of things that
would appear white to us
are brightly patterned
when birds view them,
because they have
tetrachromatic vision,
so that they see lots of
colors that we don't see
and everything else.
That's one of the
reasons that people
have argued that they're
brilliantly colored,
whereas mammals, they
smell really well.
So it's why any
of you who have--
or bad-- if any of you have ever
been in East Africa or places
like that, you know
that they always
tell you that wildebeests can
smell a lion from a couple
of kilometers away.
And it's true, because
dogs, for instance,
when they enter a
McDonald's or something,
can smell the
mustard immediately
if there's any there.
So it's a totally
different pathway for both.
Species recognition, as well
as just dealing with the world.
And birds see really well.
And I think that's what
we're seeing in these plots.
>>BALANOFF: Yeah.
They see well.
They don't smell
well, basically.
What this graph shows
you is that birds
have a very small olfactory
system relative to the rest
of their brain.
And what we see is that there's
another group of dinosaurs that
also mirrors this evolution.
Oviraptorosaurs is
the group of dinosaurs
that I've done a lot of work on.
But they also have a
very poor sense of smell.
And there's a
significant overlap
between birds and
oviraptorosaur dinosaurs,
but all of those other
non-avian coelurosaurs, things
like Archaeopteryx,
and Tyrannosaurus,
and Velociraptor, they all fall
outside of this distribution
of living birds.
So there's definitely some sort
of parallel evolution going on
between these two groups.
If you look at Incisivosaurus,
and this is in that lineage
that I just showed you,
that oviraptorosaur lineage.
Well, Incisivosaurus has a
very reduced olfactory system.
It's got very small
olfactory bulbs.
So there's something
going on there.
But finally, if you
look at Archaeopteryx,
it still has a pretty
extensive olfactory system.
So there's a complex
pattern going on,
once you get up near
the origin of birds.
There's a complex pattern
of evolution going on
with the olfactory system.
Birds, like I said, have a
very poor sense of smell.
So they have very
reduced olfactory bulbs.
And so what it looks
like is happening
is that we're having
convergent evolution,
a convergent reduction
of the olfactory system
within oviraptorosaur dinosaurs,
as well as crown group
birds or living birds.
So this is an
interesting pattern.
I don't know if we really
expected to see that.
Like I said, once we're able
to partition the brain up
into different sections,
we can look at all
these different sections.
Again, we can look
at different patterns
of how the brain is evolving
along that theropod dinosaur
lineage.
Again, a unique
pattern that we see
is that oviraptorosaur dinosaurs
have a really big cerebellum.
The cerebellum is that
part of the hind brain.
It's particularly in control
of movements, and orientation,
and things like that.
So oviraptorosaurs have a
very large cerebellum compared
to all of these other
non-avian dinosaurs,
as well as crown birds
that we were looking at.
>>NORELL: And that's one of
the things when I initially
started thinking about this
project, long-term at Amy
that I thought that yeah,
bird brains are so incredibly
big and very diverse.
And it must have something
to do with moving from a two
dimensional world to a
three dimensional world,
to have this motor
processing that you would
have to be able to
have to be able to fly,
and to be able to
navigate, and do
all these things that birds do.
At that time, we didn't have
this excellent set of fossils
to be able to show that
that's totally wrong.
But it was a good
initial starting point
to be able to do
this, to show things
like there's no way these
Oviraptors could fly.
There's no way Tyrannosaurs
could fly and stuff.
But we see this iterative
pattern and stuff
of cerebellums
much larger than we
would have ever expected
in these things that
didn't fly at all.
>>BALANOFF: This is something
that really surprised me
actually.
I didn't expect to see
oviraptorosaurs to have
such a large cerebellar volume.
And looking at the morphology
in things like Tyrannosaurus
or these more basal
taxa, you can't really
see what's going on
in the hindbrain.
And that's because they didn't
fill the brain as completely
as those specimens
or those animals that
were more close to
the origin of birds--
and then, of course, crown
group birds themselves.
And so when they don't
fill that cranial cavity,
basically what you get are
a lot of venous sinuses.
So you don't get as good a view
of what's going on in the brain
as you do within things
that do more completely fill
that cranial cavity
with their brain.
But what is going on?
What gives Oviraptorosaurs
that really huge volume
that we're seeing that
puts them above all
of the other taxa, all
the other specimens
that we were looking at?
If you can see those
lateral, these projections
off to the sides of
the cerebellum in blue,
that's something that
we call the flocculus.
And the flocculus actually has
to do with gaze stabilization.
So as things are running
around trying to catch prey,
the gaze stabilization
helps them keep focus
on what they're after.
So if it's a bug, it helps
them focus on the bug
and block out all of the
other things around them.
And so it looks
like Oviraptorosaurs
had huge floccular lobes,
which is really, again,
something I didn't
expect to see,
but something that's
definitely there
and is adding to that
cerebellar volume.
>>NORELL: And one of the
things about gaze stabilization
that's pretty interesting
in living birds
is that remember, like
I said before, not only
do birds see in more
colors than we do,
they see far better than we do.
So if you could imagine
sitting in this room
and reading like the eye chart
you have to do at the DMV,
but you're reading
it all the way down
at the end of that gallery--
a bird can do that.
A lot of birds can do that.
That's why things
like hawks and eagles
can spot little mice that
are this big from 800 feet
in the air.
>>BALANOFF: Yeah.
>>NORELL: So the
flocculus in living birds,
especially in predatory
birds, is really large.
And I think that the best way to
explain it in the digital world
and stuff, it's like
looking at a monitor,
taking a really old
monitor from 15 years ago,
and comparing that to a retinal
display on a new machine,
just how much more precise
it is when you zoom in.
And to think that the
retinal display is only
our retina-- but
the retina of a bird
is maybe three times
better or even more
than our retina is, so
that they can really see.
So this has a lot to do
with that whole floccular
area of the cerebellum.
>>BALANOFF: Yeah.
So I don't know what
oviratorosaurs were doing,
but they were very focused on
whatever they were looking for.
One final thing I want to look
at is the brain stem volume.
And again, I'm not quite
sure what's going on here.
But there's definitely
been a shift
in the size of the brain stem
from those non-avian theropods
to modern birds.
Non-avian theropods
have a much larger brain
stem than living birds do.
And the brain stem is
basically just controlling
everyday things like a
little heartbeat and things
like that, just the things
that keep you alive basically.
So the non-avian theropods
had very large brain
stems relative to living birds.
>>NORELL: And some people
have argued previously,
even on the basis of no
information, because is
the first empirical data that's
ever been shown about this,
that these subserved
bigger brain stems
had to do with body mass.
These bigger animals
would have bigger bodies.
They'd have to have
bigger brain stems
to be able to control them.
But if you look at, that there's
a lot of really small things.
Like the bottom down
there, that thing you see
should be a desert
eye and stuff.
That's half the mass of
a Thanksgiving turkey.
So we're talking still
really small animals,
but they have much
larger brain stems.
>>BALANOFF: And
then finally, this
is the really important part.
This is cerebral volume versus
total endocranial volume.
And there's a very
tight correlation
between these two variables.
This just indicates
the cerebral expansion
is incredibly important in the
expansion of the brain overall.
Cerebral expansion
started much earlier
in the history of
the avian lineage
than we initially thought.
It didn't start at
Archaeopteryx, which was
thought to be the first bird.
It didn't start at crown
group birds or living birds.
Instead, it started back here
at the base of Maniroptera.
And this is a
group that includes
dinosaurs like oviraptor
and velociraptor.
It includes Archaeopteryx
and living birds, as well.
But I think the take
home message here
is that the cerebral
expansion overall, as well
as the expansion
of the total brain
occurs much earlier
in the history
than we ever thought
it might occur.
And that's reflected in the
shape of the cerebrum as well.
Here's this Tyrannosaur.
On So this is the primitive
condition within the dinosaurs
that we're looking at.
And there's a very shallow
brain that's not very large.
It's not expanded much towards
the back of the endocast.
You see this again, that group
of dinosaurs I just mentioned,
Oviraptorosaurs.
It looks about the same.
But once you get into this
group that includes dinosaurs,
like again, microraptor,
velociraptor, Archaeopteryx--
once you get into
this group, there's
a change in the
shape of the cerebrum
as well, so that it has a
pear shape morphology to it.
There's not just an
expansion, but there's also
a change in the shape
of the cerebrum that's
going on at this point on the
evolutionary tree of dinosaurs
too.
We have these features that
are characteristic for all
of these different
groups of dinosaurs.
We have features that are
characteristic for Maniraptora.
So this is the
group that includes
Oviraptorosaur dinosaurs, plus
velociraptor, Archaeopteryx,
living birds.
We have features that
are characteristic
for Oviraptorosaurs,
as well as Paraves.
And we have characters that
are diagnostic for just
living birds.
But what's
interesting is that we
don't have characters so
far that are diagnostic
for a group called Avialae.
And that's that group that
includes Archaeopteryx
plus living birds.
So there's nothing new that
occurs at Archaeopteryx
basically.
That morphology that's
there evolved much earlier
in its history.
>>NORELL: It's one of the
things that we see iteratively
within dinosaurs.
And when I got into this
game a long time ago,
that there were birds,
and there were dinosaurs.
And now, you can't say what's
a bird and what's a dinosaur.
And 20 years ago,
if you would've
told me that we would be looking
at the brain of dinosaurs
for characters to be able to
understand their genealogy
and something about
their behavior,
I would have said
there is no chance.
But just remove it from
your head that there's birds
and there's dinosaurs.
It's just like humans
are a type of primate,
and primates are
a type of mammal.
Birds are a kind of dinosaur
and a kind of theropod dinosaur.
And the theropod dinosaurs
which are most closely related
to birds, things like
velociraptor and things
like that.
If there was one running
around down here right now,
you would just say it's
a stupid looking bird
or something, because that's
what it would look like to you.
It would behave like that.
It would act like that.
Its brain would
function like that.
It would have been
all of those things.
>>BALANOFF: Absolutely.
And so again, I think that's
the take home message from all
of this is that big brains
actually evolved much
earlier in the evolutionary
history of the avian lineage
than we thought previously.
The bird lineage starts to
expand its brain much earlier
than the onset of
powered flight.
So either it has nothing
to do with fight.
Or some of those dinosaurs,
the four winged dinosaurs
that are coming out
of China right now,
maybe they didn't
have powered flight.
But maybe they had the
neurological capacity
for some type of flight.
Like it says here, the
brain of Archaeopteryx
is really not uniquely avian.
It started much earlier in
that evolutionary history
than we previously thought.
>>NORELL: And a lot of it
is like historical baggage,
because back in the early
days of evolutionary theory,
about the same time as The
Origin of Species was written,
they found the perfect fossil.
They found the fossil
that really showed it,
because before that,
there were just types.
There were reptiles,
and there were birds.
And then two years
after Darwin published
The Origin of Species,
they dragged up
the first good
Archaeopteryx specimen.
And here was something which
was truly transitional.
It was something that
had reptilian features
as far as a long tail,
and teeth, and all
this kind of stuff.
But it clearly had feathers.
And so that was it.
So they defined that
as the first bird.
And that lasted for
about 125 years or so.
And then now, all
of a sudden, there's
all these other things--
not just feathers, but
physiology, now brains.
All these other things
have just cascaded down
the tree, and that
they've become
typical characteristics of lots
of different dinosaur groups.
So there is no such thing as a
bird separate from a dinosaur.
Take home message.
>>BALANOFF: Absolutely.
That's the point.
That's what you get from this.
But with that, I just
wanted to say, thank you
all for listening to our
whole spiel and open it up.
[APPLAUSE]
