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  • Shall I ask for a show of hands

  • or a clapping

  • I'm interested in how many

  • are three to 12 years old.

  • (Laughter)

  • None, huh?

  • All right.

  • I'm going to talk about dinosaurs.

  • Do you remember dinosaurs when you were that age?

  • (Applause)

  • Dinosaurs are kind of funny, you know.

  • (Laughter)

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

  • I hope you all realize that.

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

  • Try not to go extinct.

  • (Laughter)

  • That's it.

  • (Laughter)

  • People ask me a lot --

  • in fact, one of the most asked questions I get

  • is, why do children like dinosaurs so much?

  • What's the fascination?

  • And I usually just say,

  • "Well dinosaurs were big,

  • different and gone."

  • They're all gone.

  • Well that's not true,

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

  • So that's sort of the theme:

  • big, different and gone.

  • The title of my talk:

  • Shape-shifting Dinosaurs:

  • The Cause of a Premature Extinction.

  • Now I assume that we remember dinosaurs.

  • And there's lots of different shapes.

  • Lots of different kinds.

  • A long time ago,

  • back in the early 1900s,

  • museums were out looking for dinosaurs.

  • They went out and gathered them up.

  • And this is an interesting story.

  • Every museum wanted a little bigger or better one

  • than anybody else had.

  • So if the museum in Toronto went out

  • and collected a Tyrannosaur, a big one,

  • then the museum in Ottawa wanted a bigger one

  • and a better one.

  • And that happened for all museums.

  • So everyone was out looking

  • for all these bigger and better dinosaurs.

  • And this was in the early 1900s.

  • By about 1970,

  • some scientists were sitting around

  • and they thought, "What in the world?

  • Look at these dinosaurs.

  • They're all big.

  • Where are all the little ones?"

  • And they thought about it

  • and they even wrote papers about it:

  • "Where are the little dinosaurs?"

  • (Laughter)

  • Well, go to a museum, you'll see,

  • see how many baby dinosaurs there are.

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

  • people assumed

  • that if they had little dinosaurs,

  • if they had juvenile dinosaurs,

  • they'd be easy to identify.

  • You'd have a big dinosaur

  • and a littler dinosaur.

  • But all they had were big dinosaurs.

  • And it comes down to a couple of things.

  • First off, scientists have egos,

  • and scientists like to name dinosaurs.

  • They like to name anything.

  • Everybody likes to have their own animal that they named.

  • (Laughter)

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

  • they named it something different.

  • And what happened, of course,

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

  • In 1975,

  • a light went on in somebody's head.

  • Dr. Peter Dodson

  • at the University of Pennsylvania

  • actually realized

  • that dinosaurs grew

  • kind of like birds do,

  • which is different

  • than the way reptiles grow.

  • And in fact,

  • he used the cassowary as an example.

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

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

  • they actually grow

  • to about 80 percent adult size

  • before the crest starts to grow.

  • Now think about that.

  • They're basically retaining their juvenile characteristics

  • very late in what we call ontogeny.

  • So allometric cranial ontogeny

  • is relative skull growth.

  • So you can see

  • that if you actually found one

  • that was 80 percent grown

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

  • you would think they were two different animals.

  • So this was a problem,

  • and Peter Dodson pointed this out

  • using some duck-billed dinosaurs

  • then called Hypacrosaurus.

  • And he showed

  • that if you were to take a baby and an adult

  • and make an average of what it should look like,

  • if it grew in sort of a linear fashion,

  • it would have a crest

  • about half the size of the adult.

  • But the actual sub-adult

  • at 65 percent

  • had no crest at all.

  • So this was interesting.

  • So this is where

  • people went astray again.

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

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

  • then we would have a lot less dinosaurs

  • than we have.

  • But scientists have egos;

  • they like to name things.

  • And so they went on naming dinosaurs

  • because they were different.

  • Now we have a way of actually testing

  • to see whether a dinosaur, or any animal,

  • is a young one or an older one.

  • And that's by actually cutting into their bones.

  • But cutting into the bones of a dinosaur

  • is hard to do, as you can imagine,

  • because in museums

  • bones are precious.

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

  • They put them in foam, little containers.

  • They're very well taken care of.

  • They don't like it if you come in

  • and want to saw them open and look inside.

  • (Laughter)

  • So they don't normally let you do that.

  • But I have a museum

  • and I collect dinosaurs

  • and I can saw mine open.

  • So that's what I do.

  • (Applause)

  • So if you cut open a little dinosaur,

  • it's very spongy inside like A.

  • And if you cut into an older dinosaur,

  • it's very massive.

  • You can tell it's mature bone.

  • So it's real easy to tell them apart.

  • So what I want to do

  • is show you these.

  • In North America in the Northern Plains of the United States

  • and the Southern Plains of Alberta and Saskatchewan,

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

  • that produces the last dinosaurs that lived on Earth.

  • And there are 12 of them

  • that everyone recognizes --

  • I mean the 12 primary dinosaurs

  • that went extinct.

  • And so we will evaluate them.

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

  • So my students, my staff,

  • we've been cutting them open.

  • Now as you can imagine,

  • cutting open a leg bone is one thing,

  • but when you go to a museum

  • and say, "You don't mind if I cut open

  • your dinosaur's skull do you?"

  • they say, "Go away."

  • (Laughter)

  • So here are 12 dinosaurs.

  • And we want to look at these three first.

  • So these are dinosaurs that are called Pachycephalosaurs.

  • And everybody knows

  • that these three animals are related.

  • And the assumption is

  • is that they're related

  • like cousins or whatever.

  • But no one ever considered

  • that they might be more closely related.

  • In other words,

  • people looked at them and they saw the differences.

  • And you all know

  • that if you are going to determine

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

  • you can't do it by looking at differences, right?

  • You can only determine relatedness

  • by looking for similarities.

  • So people were looking at these

  • and they were talking about how different they are.

  • Pachycephalosaurus has a big, thick dome on its head,

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

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

  • And then Stygimoloch, another dinosaur

  • from the same age, lived at the same time,

  • has spikes sticking out the back of its head.

  • It's got a little, tiny dome,

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

  • And then there's this thing called Dracorex,

  • Hogwart's Eye.

  • Guess where that came from? Dragon.

  • So here's a dinosaur

  • that has spikes sticking out of its head, no dome

  • and gnarly stuff on its nose.

  • Nobody noticed the gnarly stuff sort of looked alike.

  • But they did look at these three

  • and they said, "These are three different dinosaurs,

  • and Dracorex is probably the most primitive of them.

  • And the other one is more primitive than the other.''

  • It's unclear to me

  • how they actually sorted these three of them out.

  • But if you line them up,

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

  • they line up like this.

  • Dracorex is the littlest one,

  • Stygimoloch is the middle size one,

  • Pachycephalosaurus is the largest one.

  • And one would think,

  • that should give me a clue.

  • (Laughter)

  • But it didn't give them a clue.

  • Because, well we know why.

  • Scientists like to name things.

  • So if we cut open Dracorex --

  • I cut open our Dracorex --

  • and look, it was spongy inside,

  • really spongy inside.

  • I mean, it is a juvenile

  • and it's growing really fast.

  • So it is going to get bigger.

  • If you cut open Stygimoloch,

  • it is doing the same thing.

  • The dome, that little dome,

  • is growing really fast.

  • It's inflating very fast.

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

  • was growing very fast as well.

  • The spikes on the back of the Stygimoloch

  • are actually resorbing,

  • which means they're getting smaller

  • as that dome is getting bigger.

  • And if we look at Pachycephalosaurus,

  • Pachycephalosaurus has a solid dome

  • and its little bumps on the back of its head

  • were also resorbing.

  • So just with these three dinosaurs,

  • you can easily -- as a scientist --

  • we can easily hypothesize

  • that it is just a growth series

  • of the same animal.

  • Which of course means