Original subtitles

NARRATOR: They keep coming out of the badlands of the world...

(mysterious music)

Each one seemingly stranger than the last.

Dinosaurs who took every imaginable body part

to extravagant extremes.

Baffling...

dazzling...

Elegant, ugly...

(dinosaur grunts)

And utterly surprising.

PHIL (off-screen): It doesn't look real.

The skull is just like something out of a science fiction movie.

♪ ♪

PAUL: They're an example of evolution gone wild.

♪ ♪

BOB (off-screen): That neck that keeps on going

and keeps on going--

that's bizarre.

(crunching)

NARRATOR: In the mysterious lost world

of the bizarre dinosaurs...

♪ ♪

Who were the strangest of the strange...

(dinosaur roars)

And how on Earth did they get that way?

♪ ♪

(dramatic music)

(dinosaur roars)

♪ ♪

(dinosaur chirps)

(mysterious music)

It may be 43 degrees in the shade--

never mind the fact that there is no shade--

but wherever the brutal sun beats down

on dinosaur territory these days,

it's a good time to be a paleontologist.

(hammer knocking)

In the 21st century,

dozens of new dinosaurs a year are coming to light.

They're not just emerging from the American west.

Now Argentina, Antarctica,

Africa, and especially China are spitting out finds

that have scientists scratching their heads.

And some of these dinosaurs are so loaded

with outlandish appendages, they're revolutionizing

what we thought we knew about them.

♪ ♪

(dinosaur roars)

But the dinosaur story doesn't start

with the bizarre and the gigantic.

150 million years before the dinosaurs' catastrophic end,

creatures like this little standard-issue prototype

had the run of the place.

Coelophysis has a rather banal body shape.

(dinosaur screeches)

It looks pretty much like a big lizard,

walks on its hind legs,

eats meat, hunts in packs.

Other than that, not much to phone home about.

(dinosaur screeches)

But paleontologists think all dinosaurs descended

from plain little animals like this guy.

(dinosaur screeching)

So how did they get from little Coelophysis

to, say, this?

Or this?

(dinosaur roars)

Or this?

♪ ♪

What strange impulses of evolution

could have molded such things?

♪ ♪

Consider the spectacular weirdness of this behemoth:

Spinosaurus...

Bigger than T. rex

but with a head that looks like a crocodile's

and stacked with spines along its back

as tall as a man.

The spines, up to 2-meter-long extensions

of the animal's vertebrae,

have been the subject of a lively debate.

♪ ♪

Some think they anchored a massive muscular hump

that would have made the enormous dinosaur

all the more powerful.

Others have suggested

that the spines supported a skin-covered sail

that could help regulate the animal's temperature

by radiating heat or catching the sun's rays.

♪ ♪

One thing is clear:

the spines must have been doing something important,

because they would have been a drag--literally.

(dinosaur roars)

PAUL: I think it would have made the animal more clumsy,

I mean, quite frankly.

It would have made it less agile.

It would have made it heavier.

It would have made it catch wind in a strong breeze.

There's no good advantage to it that you can think of

except showing that, "Hey, I can grow this 5-foot sail

"and I'm healthy and I'm bigger than you.

"And here I am over here, and there I am over there.

This is my territory. You're my mate."

NARRATOR: While most agree

that the sail was for advertising,

there's some question about Spinosaurus' general lifestyle.

Some think it was a water dweller,

where the creature may have spent most of its time.

(muffled water rushing)

Why?

Because the creature's head bears a remarkable resemblance

to that of a crocodile.

A really big crocodile.

(dramatic music)

♪ ♪

JACK (off-screen): Its snout is constructed for eating fish,

and so it's quite likely

that these animals actually were aquatic,

and so the only things that were really sticking out

that were visual-- were sticking out of the water

were these big fins on their backs.

And so, you know, much of their display

may have actually been while they were in the water.

NARRATOR: From here, the Spinosaurus puzzle

gets even more complicated.

♪ ♪

What's the use of being bigger than T. rex

if you're just going to hang out by a river and fish?

(dinosaur roars)

♪ ♪

Why have jaws powerful enough to shred another dinosaur?

Forearms armed with long, curved claws.

(dinosaur growls)

What's the evolutionary point of all these deadly developments...

(dinosaur roars)

Especially if you're going to carry a handicap on your back?

So far, Spinosaurus is keeping its secrets to itself.

PAUL (off-screen): We have never really seen anything

quite like it in the dinosaur world

or thereafter.

I mean, they're an example of evolution gone wild.

(dramatic music)

NARRATOR: Poor T. rex,

taking a back seat to Spinosaurus on the big screen.

(dinosaur growls)

But let us not forget that when it comes

to bizarre killing machines,

T. rex is in a class all of its own.

That iconic oversized head

with its 23-centimeter serrated teeth

and one of the most devastating bite forces

the world has ever seen.

And then there is that riddle of riddles:

those insanely tiny arms.

JACK (off-screen): He might have been able to scratch his belly

after he ate.

♪ ♪

That's about it.

Couldn't reach his mouth,

couldn't--couldn't clap.

Yeah, couldn't do much of anything.

NARRATOR: The T. rex head versus hands story

had a completely logical explanation--

until now.

(footsteps thundering)

It goes like this:

it has been shown over and over again

that when evolution capitalizes on one part of the anatomy,

other parts may become useless,

redundant, and eventually disappear.

(dinosaurs chirping, growling)

With a head that big and powerful and agile,

who needs arms?

(crunching)

JACK: Why does T. rex have small arms?

'Cause it didn't need them...

♪ ♪

And was probably losing them.

♪ ♪

GREG (off-screen): What appears to have happened

in the tyrannosaur lineage leading up to T. rex

is that the bodies of these animals

just kept going but the arms got left behind.

They're also losing fingers.

They've gone down to two functional fingers.

NARRATOR: This answer makes compelling sense--

at first.

♪ ♪

And T. rex was not alone

in taking this apparently sensible trade-off

in deadly assets.

♪ ♪

While the tyrant was roaming North America,

one of the weirdest-looking large predators ever

was rampaging in South America.

Called the meat-eating bull for its peculiar horns,

Carnotaurus is not pretty.

It has a strangely shaped head,

tiny teeth...

♪ ♪

And arms so small, they would make even T. rex giggle.

(dinosaur hisses)

What was it doing with them?

(dinosaur grunts, roars)

NARRATOR: The anatomy of Carnotaurus is baffling,

to say the least.

(inquisitive music)

PHIL (off-screen): Carnotaurus is one weird-looking dinosaur.

It's got a very foreshortened skull.

It looks like someone's gone up to this dinosaur

and smashed it in the face with a frying pan.

But one thing that really strikes out, though,

is this enormous shoulder blade.

It is absolutely vast.

At the end of the shoulder blade,

you'd expect to see enormous arms, but you don't.

They're absolutely tiny.

In fact, it makes the arms of Tyrannosaurus rex look large.

NARRATOR: So these great killers

living in the very last age of the dinosaurs

were apparently on the brink

of trading in their arms completely

for the sake of even more lethal heads.

♪ ♪

Makes sense, right?

But two new discoveries

have thrown a monkey wrench into that scenario

and the mystery deepens into debate.

First, you'd expect useless arms

to be, well, useless.

Instead, studies on T. rex biomechanics

show that T. rex could probably have curled

some 180 kilograms

with those pathetic-looking arms.

And now the argument that tyrannosaurus traded arms

for heads over the ages, culminating in T. rex,

is being challenged by a startling new find:

a more ancient, miniature, would-be T. rex.

The creature, though only about 3 meters long,

has already started trading arms for a head

60 million years before Tyrannosaurus rex.

PAUL (off-screen): We have found the "ur" tyrannosaur,

the roots of the tyrannosaur radiation,

an animal that has all the features

that we think are truly characteristic of tyrannosaurs:

the two-fingered hand...

the enlarged brain, the enlarged jaw muscles,

the long and lanky legs for running,

the tiny arms.

We're gonna call it Raptorex.

(curious music)

NARRATOR: The find is so new that Paul Sereno has had time

only to model Raptorex's head and neck.

(rock music)

Not as fearsome as T. rex's, perhaps,

but clearly a ferocious profile.

But it's the tiny arms that upset the apple cart.

This was supposed to be a much later development.

PAUL (off-screen): Everywhere you looked,

you found the features which we know

characterize the later tyrannosaurs

in the late Cretaceous.

They're no longer alone in having arms so small,

they couldn't reach the mouth or pick the nose.

(curious music)

NARRATOR: In other words,

if tyrannosaur arms had started to disappear

millions of generations before T. rex,

they should have been long gone

by the time the big bang snuffed them out,

traded in for even scarier heads.

(dinosaur roaring)

So why were the arms still there?

♪ ♪

Perhaps the man who named T. rex

back in 1905, Henry Fairfield Osborn,

had it right all along.

Those arms were not engineered for battle

but for love.

BOB (off-screen): He saw the big snaggly teeth

and he said, "This is for killing dinosaurs,"

and the long feet, and he said,

"This is for catching dinosaurs."

And he saw the tiny arms, and he said,

"That part is for loving."

That's the tickle part of T. rex.

(dinosaur growls)

NARRATOR: Tickling one's mate,

especially a female tyrannosaur you'd rather not upset,

makes perfectly good sense.

(dinosaurs growling)

♪ ♪

150 million years before the explosive end

to the age of the dinosaurs,

the Earth was moving beneath the dinosaurs' feet,

taking them for a ride-- literally--

into the lands of the outlandish.

Back then, all the land on Earth

was on just one continent called Pangaea.

But Pangaea started to break apart,

a geological revolution that set the stage

for an evolution revolution.

♪ ♪

The dawn of the dinosaurs, the Triassic,

was about to give way to their middle period,

the Jurassic,

and bizarreness was about to be unleashed.

♪ ♪

As the continents were moving apart,

climates were changing.

Many dinosaur havens were becoming more isolated

and more lush...

(insects chirping)

And dinosaurs were now growing

to mind-boggling sizes.

(branches snapping)

The ancient evolutionary arms race

matching predators' weapons

against prey's defenses was escalating,

with a new kind of eating machine

taking the early lead.

♪ ♪

The time of giants had arrived.

(branches snapping)

These were the sauropods.

(mysterious music)

JACK (off-screen): They basically tell us

how little we know about dinosaurs.

If we were proportioned the same way...

(dinosaur roars)

We'd have a head the size of a peanut

and it'd be suck out on the end of a 3-foot-long straw.

BOB (off-screen): That neck that keeps on going

and keeps on going--should stop but keeps on going

and going and going--

that's bizarre.

NARRATOR: One of evolution's strangest experiments

in stretching the necks of sauropods is this one:

the 20-meter, 15-ton Mamenchisaurus.

KRISTI: Its neck alone is longer than it--

the rest of its body, basically.

PAUL: When you look at the animal, it looks--

it looks disproportionate.

It looks like it's gonna fall over

because the neck is so long.

♪ ♪

NARRATOR: But an astoundingly long neck

on a ridiculously smaller body

conveys a huge advantage to an animal.

You don't have to go anywhere to eat.

Just stretch out that neck.

And no predator--even one with a brain the size of a walnut--

is going to take on such a titanic creature.

♪ ♪

KRISTI (off-screen): There's not a lot out there

that can eat a sauropod

when it's, you know, 25 feet long.

If you think about animals living in Africa today,

animals that really don't get bothered too much are elephants.

And they're huge. They're massive.

They really only have to worry about getting eaten

when they're small and when they're very old,

and I think that sauropods probably had, you know, adapted

or adopted that--that kind of similar strategy in being big.

(insects chirping)

NARRATOR: So how did the giant sauropods do it--

get so huge, they could ignore predators?

The answers lie deep in the fossilized bones

of the dinosaurs, still etched with the marks

of their life histories.

KRISTI (off-screen): One of the ways

that we can study dinosaur growth

is by looking at thin sections of dinosaur bones

so that light shines through those bones

and we can study them under a microscope

and look for these specific markers--

things like growth rings,

same kinds of things that are occurring in trees today.

NARRATOR: What these growth rings tell

Kristi Curry Rogers is nothing short of astounding.

KRISTI (off-screen): They grow between 2 and 56 times faster

than all living reptiles.

(radical rock music)

NARRATOR: You can only grow that much

if you can eat that much...

♪ ♪

And the amount an animal would have to eat

to fuel such growth is almost inconceivable.

Some of the later sauropods would multiply the efficiency

of their sweeping necks with something more:

unbelievable mouths.

(dinosaur bellows)

♪ ♪

And as Paul Sereno found out in the deserts of Niger in Africa,

by the Cretaceous, the need to feed

led some voracious plant-eaters

to evolve some seriously strange heads.

One simply blew his mind:

the lawn mower, Nigersaurus.

PAUL (off-screen): I picked up the jaw of Nigersaurus

and couldn't figure out how to attach it to the skull.

It was so strange

that it really took me quite a while to figure out

that this dinosaur had a face like no other.

♪ ♪

Only its mother really,

truly could love a dinosaur with a face like this.

NARRATOR: Ugly or not,

this face is pure genius in eating design.

Nigersaurus' curious mouth,

shaped like the flat attachment of a vacuum cleaner,

relentlessly clipped and hoovered up food

using a massive battery of small, sharp teeth.

♪ ♪

PAUL: There's no other animal that has all of its teeth

at the end of the jaw.

There's no other animal that's developed a tooth battery,

hundreds of teeth coming out at the same time.

NARRATOR: CT scans of the jawbones

showed up to nine replacement teeth

stacked behind each cutting tooth.

When one wore out,

another immediately took its place.

♪ ♪

Nigersaurus' grazing posture

may mean most or all of the sauropods

lived their lives horizontally, not vertically.

(insects chirping)

Sauropod's necks may have been more

than just a way to move insatiable mouths

over giant swaths of vegetation.

(insects chirping)

They may actually have been combat worthy,

if our long-necked friends, the giraffes,

have anything to tell us.

PAUL (off-screen): A lot of people think

that neck length in giraffes

is being driven when there's only plant matter

at the tips of the trees and the tallest giraffes

are the only ones that therefore survive.

Wrong.

Neck length is driven by mate selection,

and there's a ritual where they wrap their necks

around each other and push.

You apply that back to sauropods and you have to say,

"Well, they certainly have plenty enough neck to do that."

Uh, I'd say probably that's what they were doing.

(curious music)

(dinosaur growls)

NARRATOR: But evolution wasn't just tinkering

with the length and strength of sauropod necks.

(dinosaur growls)

♪ ♪

What exactly it was doing with this one

is a bit of a puzzle.

(dinosaur growls)

Amargasaurus,

equipped with an elegant double row of spikes

on its back, seems to have had a pair of fins.

(footsteps thudding)

One set of spines would be strange enough,

but the double row is truly baffling.

KRISTI (off-screen): Paleontologists have been

debating for years

about what the function of those spikes might have been.

NARRATOR: They're in the wrong place

to use to fight off predators.

Maybe they made the animals look much bigger

than they really were

and just intimidated the creatures

that were eyeing them hungrily.

Or maybe...

(dinosaur huffs)

They were for eyeing each other.

♪ ♪

(dinosaur bellows)

Odd structures like these are leading scientists

to a new way of thinking in paleontology.

♪ ♪

Evolution, it seems, has a strange way

of taking plain, straightforward parts of the dinosaur

with obvious functions

and turning them into garish, baffling appendages

whose purpose is the stuff of mystery and controversy.

♪ ♪

But, as always with evolution,

there's a method to the madness.

♪ ♪

Perhaps nowhere is the dinosaurs' penchant

for turning the straightforward into the fantastic more striking

than when it comes to war--

attacking others and defending themselves.

Over the course of millions of years,

intimidating weaponry sometimes morphed

into something else altogether.

Take, for example, those perennial favorites,

the stegosaurs.

Surely these creatures, with their giant plates

and spiked tails, were built to stand and fight.

(dramatic music)

What could be more obvious?

♪ ♪

Certainly, the stegosaurs bristled

with fearsome-looking armory.

♪ ♪

Take Tuojiangosaurus, one of the earliest

who took spikiness to wild extremes.

♪ ♪

A discovery from China,

Tuojiangosaurus apparently went overboard

with its defensive array.

A fearsome row of pointy plates juts out from its back,

leading down to a tail

that would give any predator or competitor pause.

♪ ♪

Four paired spikes,

each 15 centimeters long,

project from what was probably a flexible, whiplike tail.

♪ ♪

Tuojiangosaurus also sported intimidating half-meter spikes

like bayonets on its shoulders.

♪ ♪

But was this all really for battle?

Recent research on other stegosaurs

has made some scientists rethink the defense argument.

Most problematic is the plates.

They're in the wrong place.

JACK: You know, carnivorous dinosaurs

probably weren't that smart, but they probably were smart enough

to realize that if they bit the animal on the side,

they wouldn't have to deal with the spikes.

♪ ♪

NARRATOR: And the spikes and plates alone

may look intimidating, but they're not very strong

in the armory department.

♪ ♪

PAUL (off-screen): It just so happens that a few days ago,

I found a plate of a stegosaur.

A huge plate. It was massive.

And, um, when we started brushing

towards the end of the plate,

I was staggered at how thin it was.

(pensive music)

Fragile is an understatement.

♪ ♪

NARRATOR: The plates were also full of blood vessels--

not the greatest defense strategy.

Pitted against the jaws of the largest predators,

they would have been snacks.

♪ ♪

JACK (off-screen): You know, if an Allosaurus had bit

into one of them,

basically, there'd be blood spurting everywhere.

LAWRENCE: Kind of like a-- a big old cookie,

this sort of blood-filled good morsel to eat.

♪ ♪

NARRATOR: All of those blood vessels

point to another possibility:

the plates were used to regulate the animal's temperature.

♪ ♪

Arrayed to catch a breeze,

they could cool the circulation.

Pointed towards the sun, they would do the opposite.

♪ ♪

But many of the stegosaurs survived with tiny plates

or no plates at all...

(dinosaur roars)

Which leads some paleontologists to believe

that the stegosaurs' might armory--

perhaps even starting with Tuojiangosaurus--

may have become more propaganda than pointy defenses.

NARRATOR: Some argue that almost anything

you can point to as bizarre--

things like Amargasaurus' neck,

Spinosaurus' spectacular sail,

and the wondrous heads of so many favorite dinosaurs--

were all advertising:

advertising to predators that "I'm bigger than you think,"

advertising to rivals that "I'm fitter than you,"

advertising to potential mates

that "I've got the genes and health

to maintain this riot of appendages."

It's all about the display,

and display, in the end, is all about sex.

(dinosaur roars)

JACK (off-screen): Everything's for display.

An animal does not have to defend itself every year,

but it does have to mate every year.

So display is the most important thing.

Defense is secondary.

(mellow music)

MARK (off-screen): The present is the best way

to study the past.

If you look at animals today, when you see, you know,

really bizarre things--

like some of the, you know, the crests on birds

or elaborate horns on herbivorous animals

or, you know, frills on lizards and things like that--

you see, you know, 99 times out of 100

that they are display structures.

(funky music)

NARRATOR: But a quick survey of the dinosaur families

shows that we've left something out.

♪ ♪

-Those heads. -(dinosaur roars)

So many of them were ominously horned,

spiked,

collared,

crested...

and domed.

(dinosaur grunts)

Surely these were meant for violence

against predators and rivals, right?

In the world of the bizarre dinosaurs,

apparently, nothing is as it seems.

♪ ♪

(dramatic music)

(frogs chirping)

Sex:

it's what it's all about.

♪ ♪

In the natural world, either you've got what it takes

to find, fight for, and win over a mate,

or you're Darwin-ed out of the race.

No more genes.

♪ ♪

By the time we've reached the Cretaceous,

especially as the dinosaurs' doom descended

at the very end,

evolution had designed some of the most flamboyant

and creative sexual displays and behaviors

the world has ever seen.

And the key to success was often using your head.

♪ ♪

When it comes to perplexing head gear,

nothing could top the ceratopsians,

bearing some of the most fearsome heads

to grace the prehistoric world.

♪ ♪

They certainly look like weapons and armory:

sharp spears sticking out of broad shields.

♪ ♪

Take, for example, our old favorite:

triple-horned and elegantly collared Triceratops,

often depicted fending off a voracious T. rex.

(film reel clicking)

For Jack Horner, this is not a terribly convincing scenario.

JACK: From a logical point of view,

the last place in this world you want your defense mechanism

is on your head.

I mean, about the time you poke a hole

in a T. rex and he falls down,

he's gonna land on top of your head.

(dramatic rock music)

(horns crack)

(horns clatter)

♪ ♪

(moose bellowing)

♪ ♪

(horns clatter)

♪ ♪

NARRATOR: So what about another obvious solution:

that they were fighting each other,

that all of this headgear

was mostly about testosterone-drenched males

pounding the living daylights out of each other

in the fight for mating rights?

♪ ♪

Certainly among some amorous mammals today,

head-on violence seems to be a prerequisite

for reproductive success.

♪ ♪

(curious music)

Even among the reptiles today,

there are a handful of headbutters,

and one of them, the Jackson's chameleon,

looks startlingly like its ancient distant cousin.

GREG: Here's your Triceratops analogy.

I mean, look at it. Three horns.

Unbelievable.

Even has a--what they call a cask.

This is very much like the frill

on the back of a horned dinosaur

such as, uh, Triceratops.

And there is some evidence of injuries

on the frills of Triceratops

that suggests that they did fight with one another.

NARRATOR: But chameleons would rather display their horns

than lock them,

and Greg Erickson thinks

the ceratopsians would have done the same.

GREG (off-screen): What were these structures for?

Well, the traditional explanation

is that this shield was a defense

to parry off blows from other horned dinosaurs

or to help and protect their neck

when they were being attacked by predatory dinosaurs.

And I'm not sure I believe any of that.

I think these are display structures, for the most part.

♪ ♪

NARRATOR: From humble origins in the Jurassic,

the ceratopsians' heads simply exploded

into exuberant spectacles in their last days.

There's our favorite, Triceratops,

along with its even more outlandish cousins.

There's Styracosaurus, meaning "spiked lizard,"

with its profusion of long horns

extending from its neck frill.

Here's elegant Chasmosaurus,

with an even taller, more elegant frill,

this one edged with lacy little spikes.

And the equally curious head of Centrosaurus.

♪ ♪

For many paleontologists today,

these extreme heads are a clear indication

that the ceratopsians were lovers, not fighters.

♪ ♪

Potential mates could recognize their own kind at a distance,

size up their frills,

and get to the heart of the matter.

To heighten the allure,

the heads may have blazed with colors

as extravagant as their sizes and shapes.

In one dinosaur family,

the question of how best to use your head

to win the girl has reached its own level of weirdness,

one in which headbutting among paleontologists

is getting fiercer than any head-banging

in the Mesozoic.

Welcome to the world of the pachycephalosaurs,

or "thick-headed lizards."

(footsteps thudding)

If any animal on Earth looks more suited

to slamming its cranium into another's,

it has got to be some of these guys.

Some of their domes are 20 centimeters thick or more,

inspiring awe and controversy in equal measure.

BOB (off-screen): Of all the major dinosaur groups,

the butt-heads are the ones

that inspire the deepest soul-searching among us,

the most puzzled expressions,

and the most extraordinary, exhilarating flights of idiocy.

PAUL: We're in a struggle

to understand dome-headed dinosaurs.

JACK: Adult pachycephalosaur domes

are definitely not adapted for headbutting.

Definitely not.

NARRATOR: On one point, everyone agrees:

the heads of the pachycephalosaurs

were sexy-- at least to other pachys.

The argument is over whether they were sexy

in the violent sense--impressing the females with power--

or pure visual allure.

(dinosaur grunts)

(curious music)

There's no doubt that the skull of this dome-head--

Pachycephalosaurus-- bears a striking resemblance

to the most dedicated headbutters of today.

BOB (off-screen): This is the butt-head supreme alive today.

♪ ♪

The musk ox.

Side view.

Big googly eyes, dome here--

please note, it is domed.

67 million years ago, this rammed.

Right now in the Arctic tundra, this rams.

NARRATOR: But for Jack Horner, even if a head

looks on the outside like it was used for butting,

you have to look inside to see if it was up to the job.

He has been cutting open the heads

of pachycephalosaurs for years now.

What he has found was counterintuitive.

Their heads were full of brittle stuff.

(inquisitive music)

JACK (off-screen): They're constructed

of a very odd kind of bone.

It is brittle; it's kind of like porcelain.

And if those dinosaurs had crashed their heads together,

they probably would have just shattered.

The pachys did not headbutt

and couldn't have more than once.

Once they crashed their heads together,

that would have knocked them both out

and they'd have just been laying there.

(dinosaurs grunting)

NARRATOR: For Jack Horner, then,

the pachycephalosaur heads

were all about the same old love song:

a pure display of health and vitality

with no need for all of that violence.

(dramatic rock music)

Not everyone is convinced.

♪ ♪

Earlier studies indicate the bones were pretty sturdy

and awfully biologically expensive

for just showing off.

♪ ♪

PAUL (off-screen): 6, 7, 8 inches of solid bone

in some of these large pachycephalosaur dinosaurs.

That's a lot of bone to feed, a lot of bone to upkeep.

NARRATOR: And even if head-banging

may have taken its toll, it would have been worth it.

♪ ♪

BOB (off-screen): If you're gonna headbutt

to impress a potential mate,

you're gonna run the risk of breaking your head.

It does happen today with musk oxen,

and it's a risk you've got to take

because that's the only way to get your genes

into the next generation.

NARRATOR: Bob Bakker points out two other factors.

Like the musk ox,

pachycephalosaurs have huge areas

on the back of the neck

where massive muscles could have been attached.

♪ ♪

And then there's that equally classic dinosaur brain.

BOB: Though I love these animals,

they were dumb as posts.

The brain is very small.

Small brains are harder to injure.

(dramatic music)

NARRATOR: The headbutting--

among both dinosaurs and paleontologists--

reaches its culmination

with one of the most bizarre dinosaurs of all.

Enter the dragon...

(dinosaur calling)

Dracorex hogwartsia.

PHIL (off-screen): What makes Dracorex hogwartsia so wonderful

is, it does look like something out of a fantasy movie.

It really does look like a dragon

with this strange spiky skull.

It doesn't look real.

NARRATOR: If ever there was a face made for headbutting,

as far as Bob Bakker's concerned,

it's this one.

It bears a remarkable resemblance

to the head-banging African warthog,

and by mashing two casts

of Dracorex's peculiar face together,

he discovered something amazing.

BOB: This is craniological Velcro.

There are so many bumps that you press the heads together

and they don't slip.

So they push and shove and push and shove

and push and shove until one of them gives up.

NARRATOR: Even here, opinions differ.

Horner suspects that Dracorex wasn't even its own species,

let alone a headbutter,

just an adolescent pachycephalosaur

obviously going through an awkward phase.

Clearly, the dragon king of hogwartsia

is not going to put the headbutting controversy to rest.

♪ ♪

And now an even more puzzling little dinosaur

has charged into the debate:

a dome-headed mini pachycephalosaur

about the size of a cat.

PAUL: We have found an absolutely bizarre headbutter

that we believe is a dwarf.

(quirky music)

A little animal we're gonna call Mushroom Head, Microcephale,

because it almost looks like it's wearing

a top hat that's expanded

yet it's filled with solid bone...

♪ ♪

Covered with an armored surface that also is smooth at the top.

NARRATOR: A headbutter this small?

Surely it was just a baby pachy.

Except the CT scans told a different story.

♪ ♪

The sutures between the bones in its skull

had completely fused,

which means the animal was a full-grown adult.

♪ ♪

PAUL: I think this is our smallest headbutter

ever to have evolved.

(dinosaurs grunting)

NARRATOR: From the violent

to the most peaceful way to use your head,

here is a creature that may have perfected

that gentlest of seductions...

(dinosaur bugles)

The love song.

(dinosaur bugles)

The curiously crested head of Parasaurolophus

kept paleontologists guessing for generations.

(dinosaurs bugling)

PHIL (off-screen): Parasaurolophus

is just truly weird.

It's got this enormous expansion of skull bones

which projects into this banana-like lump

coming out of the back of its skull.

(dramatic music)

NARRATOR: For a long time, it was assumed

that this dinosaur was a water dweller

and used its unusual headgear as a snorkel.

♪ ♪

But CT scans of the crest

show that there was no opening at the top to breathe through.

What those CT scans did show was this...

An elegant construction of tubes

that bears a striking resemblance to a trombone.

♪ ♪

Using the CT scans

to generate a 3-D virtual instrument,

scientists in New Mexico

may have even re-created Parasaurolophus' eerie music.

(dinosaur bugling)

In fact, its crest might have done double duty

when it came to flirting,

displaying both audibly and visually

for the opposite sex.

(dinosaur bugling)

♪ ♪

(mysterious music)

♪ ♪

Though the arguments about exactly how dinosaurs

used their heads just keep heating up,

one thing is for sure:

sex in the late Cretaceous...

(dinosaur roars)

Was a roaring success.

But the wild triumphs of the age of the dinosaurs

were about to be rendered moot.

Their only hopes rested with an evolutionary experiment

that would result in some of the most baffling creatures ever.

♪ ♪

(dramatic music)

NARRATOR: After more than 150 million years

dominating the Earth, the dinosaurs were doomed.

♪ ♪

There was an asteroid on the way.

Volcanoes were about to explode.

Perhaps even a deadly plague was being unleashed.

♪ ♪

But evolution had nonetheless stumbled onto a plan

for the dinosaurs' survival:

the bird plan.

♪ ♪

And nature's experiments with the bird cousins

were simply wild.

(curious music)

Take this little birdlike dinosaur...

♪ ♪

Epidendrosaurus.

♪ ♪

Standing on two legs with forearms and claws

elongating into winglike proportions

and possibly sporting feathers,

sparrow-sized Epidendrosaurus couldn't fly,

but it probably did live in trees,

where its outrageous hands came in, well, handy.

♪ ♪

They are completely out of proportion to its body,

and that one finger is twice as long as the others.

MARK: I mean, it's sort of similar to what you see

in this type of lemur called an aye-aye in Madagascar,

where that really elongated finger

may have been used to, you know,

dig into the bark of trees after termites

or some other insects that they were eating.

You know, that's also a very, very strange thing.

♪ ♪

Three, four, five, six.

NARRATOR: More than a decade ago,

Mark Norell discovered some of the first direct evidence

of birdlike behavior among the dinosaurs...

MARK: 12 eggs.

(inhales sharply) All right.

NARRATOR: Fossilized dinos

who had been sitting on their fossilized eggs.

♪ ♪

These were the oviraptors.

(dramatic music)

Most oviraptors looked like birds

and stuck to birdlike sizes,

the largest being smaller than an ostrich.

♪ ♪

That is, until this behemoth was discovered:

Gigantoraptor...

more than 5 meters tall

and weighing in at 1 1/2 tons.

PHIL: This was absolutely enormous.

This was a big animal.

It's almost on the scale of Tyrannosaurus rex,

but think scaling a giant chicken.

This is what this animal almost looked like.

♪ ♪

NARRATOR: This enormous dinosaur has a toothless beak,

which would suggest that it ate plants,

but its size and fearsome claws

hint that it may have been a meat-eater as well.

♪ ♪

(dinosaur squawking)

♪ ♪

But perhaps the most mysterious birdlike dinosaur of all

is this one: Deinocheirus.

Known only from a single set of tremendous arms and claws,

the animal may have been 12 meters long.

♪ ♪

Originally imagined to be a deadly carnivore

tearing its prey to shreds with those incredible claws,

Deinocheirus may actually have been a gentle giant.

Some paleontologists think that it may have behaved

more like that most placid of animals, the sloth.

But until some more of its intriguing fossils are found,

Deinocheirus is largely a creature of the imagination.

♪ ♪

Deinocheirus lived at the end of the Cretaceous period

and may well have been around to witness the cataclysmic end

to the age of the dinosaurs.

(explosion)

(rumbling)

(dinosaur chirps)

Its line did not survive.

(rumbling)

But some little dino birds did, and no one knows why.

It is one of the greatest mysteries

in the dinosaurs' riddle-filled story.

(mysterious music)

All we do know is that the basic body plan--

the bird plan-- somehow made it through

to the modern age,

and the birds of today

are now the bizarre dinosaurs of the world.

Far more successful than either mammals or reptiles,

the birds have managed to find ways to thrive

in virtually every habitat on Earth.

(penguins chirping)

And nothing can match them

in terms of outrageous behavior

and spectacular displays of strength and sexiness.

They're a credit to their extraordinary predecessors,

ancient cousins

who seemed to take every opportunity to stretch

the bounds of nature's creativity.

KRISTI (off-screen): They evolved horns,

frills, spikes, plates,

long necks, long tails,

sharp claws, big teeth.

They do all of these things

and they're wildly successful organisms on the planet

from 228 million years ago to 65 million years ago.

They are the kings and queens of the Earth at that time.

(pensive music)

NARRATOR: And the truly remarkable part?

We've probably only discovered a tiny fraction

of all the dinosaurs that ever existed.

♪ ♪

Meaning that even more mind-boggling

and mystifying creatures are out there

just waiting to be found.

♪ ♪

MARK (off-screen): This amazing amount of material we find,

some of it's going to be some very unusual animals,

so it was probably a lot weirder in the past

than we can even imagine.

PAUL (off-screen): That's the fun part of paleontology

because you can be assured of this: that we're gonna find

some new and bizarre dinosaurs in the future.

♪ ♪

JACK (off-screen): There are plenty of surprises out there,

so many things that you can't predict.

All I can say is, you know, be ready for anything.

(dinosaurs grunting)

(dinosaurs growling, bugling)

♪ ♪

Captioned by Captionmax