WEBVTT

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Shall I ask for a show
of hands or a clapping

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of people in different generations?

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I'm interested in how many
are three to 12 years old.

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(Laughter)

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None, huh?

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(Laughter)

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All right.

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I'm going to talk about dinosaurs.

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Do you remember dinosaurs
when you were that age?

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(Applause)

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Dinosaurs are kind of funny, you know.

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(Laughter)

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We're going to kind of go
in a different direction right now.

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I hope you all realize that.

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So I'll just give you my message up front:

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Try not to go extinct.

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(Laughter)

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That's it.

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(Laughter)

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People ask me a lot --

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in fact, one of the most asked
questions I get

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is, why do children
like dinosaurs so much?

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What's the fascination?

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And I usually just say,

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"Well, dinosaurs were big,

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different and gone."

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They're all gone.

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Well that's not true,

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but we'll get to the goose in a minute.

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So that's sort of the theme:

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big, different and gone.

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The title of my talk:

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Shape-shifting Dinosaurs:

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The cause of a premature extinction.

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Now I assume that we remember dinosaurs.

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And there's lots of different shapes.

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Lots of different kinds.

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A long time ago,

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back in the early 1900s,
museums were out looking for dinosaurs.

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They went out and gathered them up.

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And this is an interesting story.

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Every museum wanted a little bigger
or better one than anybody else had.

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So if the museum in Toronto went out
and collected a Tyrannosaur, a big one,

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then the museum in Ottawa
wanted a bigger one, and a better one.

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And that happened for all museums.

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So everyone was out looking
for all these bigger and better dinosaurs.

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And this was in the early 1900s.

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By about 1970,

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some scientists were sitting around
and they thought, "What in the world --

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Look at these dinosaurs, they're all big.

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Where are all the little ones?"

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(Laughter)

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And they thought about it
and they even wrote papers about it:

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"Where are the little dinosaurs?"

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(Laughter)

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Well, go to a museum, you'll see,

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see how many baby dinosaurs there are.

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People assumed --
and this was actually a problem --

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people assumed
that if they had little dinosaurs,

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if they had juvenile dinosaurs,
they'd be easy to identify.

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You'd have a big dinosaur
and a littler dinosaur.

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(Laughter)

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But all they had were big dinosaurs.

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And it comes down to a couple of things.

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First off, scientists have egos,

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and scientists like to name dinosaurs.

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They like to name anything.

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Everybody likes to have
their own animal that they named.

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(Laughter)

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And so every time they found something
that looked a little different,

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they named it something different.

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And what happened, of course,

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is we ended up with a whole
bunch of different dinosaurs.

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In 1975,

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a light went on in somebody's head.

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Dr. Peter Dodson
at the University of Pennsylvania

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actually realized that dinosaurs
grew kind of like birds do,

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which is different
than the way reptiles grow.

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And in fact,

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he used the cassowary as an example.

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And it's kind of cool --
if you look at the cassowary,

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or any of the birds
that have crests on their heads,

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they grow to about 80 percent adult size
before the crest starts to grow.

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Now think about that.

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They're basically retaining
their juvenile characteristics

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very late in what we call ontogeny.

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So allometric cranial ontogeny
is relative skull growth.

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So you can see that if you actually found
one that was 80 percent grown

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and you didn't know that it was going
to grow up to a cassowary,

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you would think
they were two different animals.

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So this was a problem,

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and Peter Dodson pointed this out
using some duck-billed dinosaurs

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then called Hypacrosaurus.

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And he showed that if you were to take
a baby and an adult

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and make an average
of what it should look like,

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if it grew in sort of a linear fashion,

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it would have a crest
about half the size of the adult.

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But the actual subadult at 65 percent
had no crest at all.

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So this was interesting.

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So this is where people went astray again.

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I mean, if they'd have just taken that,

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taken Peter Dodson's work,
and gone on with that,

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then we would have a lot less
dinosaurs than we have.

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But scientists have egos;
they like to name things.

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And so they went on naming dinosaurs
because they were different.

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Now we have a way of actually testing

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to see whether a dinosaur, or any animal,
is a young one or an older one.

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And that's by actually
cutting into their bones.

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But cutting into the bones of a dinosaur
is hard to do, as you can imagine,

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because in museums, bones are precious.

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You go into a museum,
and they take really good care of them.

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They put them in foam, little containers.

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They're very well taken care of.

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They don't like it if you come in
and want to saw them open and look inside.

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(Laughter)

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So they don't normally let you do that.

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(Laughter)

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But I have a museum
and I collect dinosaurs

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and I can saw mine open.

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So that's what I do.

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(Applause)

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So if you cut open a little dinosaur,

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it's very spongy inside, like A.

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And if you cut into an older dinosaur,
it's very massive.

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You can tell it's mature bone.

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So it's real easy to tell them apart.

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So what I want to do is show you these.

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In North America in the northern plains
of the United States

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and the southern plains
of Alberta and Saskatchewan,

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there's this unit of rock
called the Hell Creek Formation

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that produces the last
dinosaurs that lived on Earth.

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And there are 12 of them
that everyone recognizes --

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I mean the 12 primary dinosaurs
that went extinct.

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And so we will evaluate them.

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And that's sort of what I've been doing.

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So my students, my staff,
we've been cutting them open.

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Now as you can imagine,
cutting open a leg bone is one thing,

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but when you go to a museum

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and say, "You don't mind if I cut open
your dinosaur's skull, do you?"

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they say, "Go away."

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(Laughter)

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So here are 12 dinosaurs.

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And we want to look at these three first.

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So these are dinosaurs
that are called Pachycephalosaurus.

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And everybody knows
that these three animals are related.

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And the assumption is that they're related
like cousins or whatever.

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But no one ever considered
that they might be more closely related.

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In other words,

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people looked at them
and they saw the differences.

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And you all know
that if you are going to determine

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whether you're related
to your brother or your sister,

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you can't do it by looking at differences.

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You can only determine relatedness
by looking for similarities.

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So people were looking at these

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and they were talking
about how different they are.

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Pachycephalosaurus has a big,
thick dome on its head,

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and it's got some little bumps
on the back of its head,

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and it's got a bunch of gnarly things
on the end of its nose.

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And then Stygimoloch, another dinosaur
from the same age, lived at the same time,

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has spikes sticking out
the back of its head.

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It's got a little, tiny dome,

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and it's got a bunch
of gnarly stuff on its nose.

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And then there's this thing
called Dracorex hogwartsia.

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Guess where that came from?

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Dragon.

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So here's a dinosaur that has spikes
sticking out of its head,

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no dome and gnarly stuff on its nose.

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Nobody noticed the gnarly stuff
sort of looked alike.

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But they did look at these three

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and they said, "These
are three different dinosaurs,

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and Dracorex is probably
the most primitive of them.

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And the other one
is more primitive than the other."

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It's unclear to me how they actually
sorted these three of them out.

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But if you line them up,

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if you just take those three skulls
and just line them up,

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they line up like this.

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Dracorex is the littlest one,

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Stygimoloch is the middle-size one,

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Pachycephalosaurus is the largest one.

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And one would think,
that should give me a clue.

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(Laughter)

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But it didn't give them a clue.

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(Laughter)

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Because, well we know why.

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Scientists like to name things.

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So if we cut open Dracorex --

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I cut open our Dracorex --

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and look, it was spongy inside,
really spongy inside.

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I mean, it is a juvenile
and it's growing really fast.

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So it is going to get bigger.

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If you cut open Stygimoloch,
it is doing the same thing.

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The dome, that little dome,
is growing really fast.

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It's inflating very fast.

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What's interesting is the spike
on the back of the Dracorex

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was growing very fast as well.

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The spikes on the back of the Stygimoloch
are actually resorbing,

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which means they're getting smaller
as that dome is getting bigger.

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And if we look at Pachycephalosaurus,

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Pachycephalosaurus has a solid dome

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and its little bumps on the back
of its head were also resorbing.

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So just with these three dinosaurs,

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as a scientist, we can easily hypothesize

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that it is just a growth series
of the same animal.

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Which of course means

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that Stygimoloch and Dracorex are extinct.

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(Laughter)

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OK.

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(Laughter)

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Which of course means
we have 10 primary dinosaurs to deal with.

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So a colleague of mine at Berkeley --
he and I were looking at Triceratops.

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And before the year 2000 --

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now remember, Triceratops was first
found in the 1800s --

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before 2000, no one had ever seen
a juvenile Triceratops.

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There's a Triceratops
in every museum in the world,

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but no one had ever collected a juvenile.

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And we know why, right?

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Because everybody wants to have a big one.

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So everyone had a big one.

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So we went out and collected
a whole bunch of stuff

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and we found a whole bunch of little ones.

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They're everywhere,
they're all over the place.

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So we have a whole bunch
of them at our museum.

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(Laughter)

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And everybody says
it's because I have a little museum.

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When you have a little museum,
you have little dinosaurs.

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(Laughter)

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If you look at the Triceratops,

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you can see it's changing,
it's shape-shifting.

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As the juveniles are growing up,
their horns actually curve backwards.

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And then as they get older,
the horns grow forward.

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And that's pretty cool.

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If you look along the edge of the frill,

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they have these little triangular bones
that actually grow big as triangles

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and then they flatten against the frill

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pretty much like the spikes do
on the Pachycephalosaurs.

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And then, because the juveniles
are in my collection,

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I cut them open ...

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(Laughter)

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and look inside.

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And the little one is really spongy.

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And the middle-size one is really spongy.

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But what was interesting
was the adult Triceratops was also spongy.

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And this is a skull
that is two meters long.

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It's a big skull.

NOTE Paragraph

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But there's another dinosaur
that is found in this formation

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that looks like a Triceratops,
except it's bigger,

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and it's called Torosaurus.

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And Torosaurus, when we cut
into it, has mature bone.

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But it's got these big
holes in its shield.

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And everybody says,

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"A Triceratops and a Torosaurus
can't possibly be the same animal

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because one of them's bigger
than the other one."

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(Laughter)

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"And it has holes in its frill."

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And I said, "Well do we have
any juvenile Torosauruses?"

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And they said, "Well, no,
but it has holes in its frill."

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So one of my graduate
students, John Scannella,

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looked through our whole collection

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and he actually discovered that the hole
starting to form in Triceratops

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and, of course it's open, in Torosaurus --

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so he found the transitional ones
between Triceratops and Torosaurus,

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which was pretty cool.

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So now we know that Torosaurus
is actually a grown-up Triceratops.

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Now when we name dinosaurs,

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when we name anything,
the original name gets to stick

00:14:55.328 --> 00:14:59.173
and the second name is thrown out.

00:14:59.936 --> 00:15:02.128
So Torosaurus is extinct.

00:15:03.441 --> 00:15:07.259
Triceratops, if you've heard the news,
a lot of the newscasters got it all wrong.

00:15:07.283 --> 00:15:10.833
They thought Torosaurus should be kept
and Triceratops thrown out,

00:15:10.857 --> 00:15:12.641
but that's not going to happen.

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00:15:12.665 --> 00:15:18.155
(Laughter)

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00:15:18.179 --> 00:15:21.462
All right, so we can do this
with a bunch of dinosaurs.

00:15:21.486 --> 00:15:23.532
I mean, here's Edmontosaurus

00:15:23.556 --> 00:15:24.976
and Anatotitan.

00:15:25.423 --> 00:15:27.975
Anatotitan: giant duck.

00:15:28.632 --> 00:15:30.783
It's a giant duck-bill dinosaur.

00:15:30.807 --> 00:15:32.535
Here's another one.

00:15:32.559 --> 00:15:35.032
So we look at the bone histology.

00:15:35.056 --> 00:15:39.939
The bone histology tells us
that Edmontosaurus is a juvenile,

00:15:39.963 --> 00:15:41.591
or at least a subadult,

00:15:41.615 --> 00:15:47.368
and the other one is an adult,
and we have an ontogeny.

00:15:48.273 --> 00:15:50.226
And we get rid of Anatotitan.

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00:15:51.400 --> 00:15:53.221
So we can just keep doing this.

00:15:53.245 --> 00:15:56.581
And the last one is T. Rex.

00:15:57.332 --> 00:16:01.976
So there's these two dinosaurs,
T. Rex and Nanotyrannus.

00:16:02.000 --> 00:16:04.890
(Laughter)

00:16:04.914 --> 00:16:07.630
Again, it makes you wonder.

00:16:07.654 --> 00:16:10.864
(Laughter)

00:16:10.888 --> 00:16:13.223
But they had a good question.

00:16:13.247 --> 00:16:16.132
They were looking at them and they said,
"One's got 17 teeth,

00:16:16.156 --> 00:16:18.020
and the biggest one's got 12 teeth.

00:16:18.044 --> 00:16:19.914
And that doesn't make any sense at all,

00:16:19.938 --> 00:16:23.606
because we don't know of any dinosaurs
that gain teeth as they get older.

00:16:23.630 --> 00:16:25.878
So it must be true --

00:16:25.902 --> 00:16:27.195
they must be different."

00:16:28.643 --> 00:16:29.976
So we cut into them.

00:16:31.373 --> 00:16:35.250
And sure enough,
Nanotyrannus has juvenile bone

00:16:35.274 --> 00:16:38.866
and the bigger one has more mature bone.

00:16:39.439 --> 00:16:41.842
It looks like it could still get bigger.

00:16:41.866 --> 00:16:44.087
And at the Museum
of the Rockies where we work,

00:16:44.111 --> 00:16:47.750
I have four T. rexes,
so I can cut a whole bunch of them.

00:16:47.774 --> 00:16:49.976
But I didn't have to cut
any of them really,

00:16:50.000 --> 00:16:52.976
because I just lined up their jaws

00:16:53.000 --> 00:16:56.310
and it turned out
the biggest one had 12 teeth

00:16:56.334 --> 00:16:58.509
and the next smallest one had 13

00:16:58.533 --> 00:17:00.763
and the next smallest had 14.

00:17:00.787 --> 00:17:02.810
And of course, Nano has 17.

00:17:02.834 --> 00:17:05.721
And we just went out and looked
at other people's collections

00:17:05.745 --> 00:17:09.480
and we found one that has
sort of 15 teeth.

00:17:09.504 --> 00:17:12.282
So again, real easy to say

00:17:12.306 --> 00:17:16.975
that Tyrannosaurus ontogeny
included Nanotyrannus,

00:17:17.686 --> 00:17:22.325
and therefore we can take out
another dinosaur.

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00:17:22.349 --> 00:17:23.976
(Laughter)

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00:17:27.377 --> 00:17:30.670
So when it comes down
to our end Cretaceous,

00:17:30.694 --> 00:17:32.241
we have seven left.

00:17:34.099 --> 00:17:35.384
And that's a good number.

00:17:35.756 --> 00:17:38.976
That's a good number
to go extinct, I think.

00:17:39.604 --> 00:17:40.838
Now as you can imagine,

00:17:40.862 --> 00:17:43.623
this is not very popular
with fourth-graders.

00:17:43.743 --> 00:17:44.744
(Laughter)

00:17:44.768 --> 00:17:49.744
Fourth-graders love their dinosaurs,
they memorize them.

00:17:53.113 --> 00:17:54.843
And they're not happy with this.

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00:17:54.867 --> 00:17:57.483
(Laughter)

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00:17:57.507 --> 00:17:58.698
Thank you very much.

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00:17:58.722 --> 00:18:02.626
(Applause)