David Attenborough's Conquest of the Skies 3D Page #2

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it has this great flange.

And Pterosaur skeletons

from other species

have been found, some with such flanges

but others without.

So it's thought that maybe

this was the difference

between the sexes.

Maybe was the male

that had these big flanges

at the back which it displayed them,

and maybe it was covered with skin,

we can only guess.

Many different Pterosaur species

evolved these headcrests,

and seems very likely,

that they were coloured.

This spectacular example,

is known as Tapejara.

And it made its home beside inland lakes.

But Pterosaurs diversified

in other ways too.

Some evolved much larger bodies.

This species had a wingspan

of over 20 feet, 7 metres.

But not all Pterosaurs

lived in the forests or near water.

An open, arid landscape like this one,

was the likely home

of one of the most extraordinary.

Around 70 million years ago,

a Pterosaur appeared

that was of truly colossal proportions.

That was one of the largest creatures

that has ever flown,

it was in the size of a small aeroplane,

and it was called, Quetzalcoatlus.

Its immense wingspan allowed it

to ride on the currents of warm air

that rise up from sun-heated land.

It could then glide great distances,

searching for food.

Small creatures like lizards,

or the dead bodies

of much larger ones, dinosaurs.

But the Pterosaurs,

with their wings of toughened skin,

weren't the only group of reptiles

to make it into those ancient skies.

About 150 million years ago,

another reptilian group appeared

on the planet that also flew.

Like most reptiles, including Pterosaurs,

these creatures began their lives

inside an egg.

But they had evolved

a revolutionary new design for flight,

one that would usher in

a remarkable fresh chapter, in our story.

And unlike the Pterosaurs,

they're still with us today.

There are of course, the birds.

Some today can provide clues,

about how their ancestors

managed to get into the air.

This is the chick of a bird

found in farmyards everywhere:

A Bantam Hen.

And at this very early stage in its life,

it can show us something very interesting

about the origin of that crucial piece

of flying equipment, a feather.

Its feathers are downy, that's to say,

they're made up of simple filaments,

and their function is not for flight,

but insulation,

to keep this little creature warm.

And back in the Jurassic period,

long before the arrival of true birds,

very similar looking feathers

appeared on very different animals,

reptiles, dinosaurs to be precise.

To find evidence

for that astonishing statement,

which not so long ago was highly

controversial, we're heading for China.

Northeast of China's Great Wall,

near the borders of Mongolia,

lies the chilly province of Liaoning.

Here, there are great areas

of rocks that were laid down as mud,

in the bottom of immense

fresh water lakes.

The bodies of animals that

were swept down into these lakes,

were slowly entombed

by the fine-grained sediment

that preserved them entire

and in exquisite detail.

And from these rocks have come specimens

that solve one of the most hotly debated

of evolutionary arguments:

The origin of the birds.

The key specimens are now in Beijing,

where they've been delicately prepared,

under the microscope.

They have been studied here, by one

of the world greatest dinosaur experts,

Professor Xing Xu.

First, he showed me

one of his oldest specimens,

part of a dinosaur's arm.

But thanks to the fineness

of the mud of those ancient lakes,

there is more here than just bones.

You see here, this species

is called a Beipiaosaurus,

So because this is an animal

like two or three metres long,

so quite a big animal. And here

is an arm, hand, you see here...

dark filamentous structures...

- Yes.

along that arms and hand,

they're actually primitive feathers.

And those feathers are very simple,

very very simple,

so we believe they represent

the very primitive stage

for feather evolution.

These simple strands were made

of the same material,

as the feathers of today birds.

They were relatively thick,

and must have been quite stiff,

so they would have stuck out

beyond the dinosaur's arm.

Behind them, were shorter strands

that covered its whole body.

Like the down on the chick,

these might have kept the dinosaur warm.

But those long strands most likely

had a different function.

Clues to what that

might have been can be found

on an even more extraordinary fossil.

These claws and finger bones belong

to a creature called Caudipteryx.

The long dark shapes around them,

are the remains of feathers.

The single strands are here

rather more complex.

They had barbs, thin filaments attached

to either side of a central rod.

This looks more like a bird's feather.

Caudipteryx had around 26 of them,

along each arm.

This may look like a wing,

but the feathers were not very long.

And when you compare them

to the size of this creature's body,

and its long legs, it's clear

that they weren't big enough

to enable Caudipteryx to fly.

So, what were these feathers for?

Microscopic examination has revealed

that they were coloured, and patterned.

So, maybe they were used for display,

perhaps to wave around

during courtship, to attract a mate.

But then is seems that they also

helped the dinosaur, in a different way.

We can find a hint of how

they might have done this,

by watching the way some young birds

use their first feathers today.

These are ten day old Pheasant chicks.

Their feathers are

not yet fully developed.

At this stage they're similar

in structure, to the feathers

on that dinosaur, Caudipteryx,

and grow in a line along each arm,

in much the same way.

But these early feathers

are also too short,

to enable these creatures to fly.

Nevertheless, they're very helpful.

Pheasant chicks hatch

in nests on the ground,

but they soon need to roost high up,

where they'll be safe from predators.

Flapping these simple wings

gives the chicks a little extra lift,

to help them climb into a tree.

And when the time comes

to return to the ground,

those first feathers again, are a help.

They don't provide a large

air-catching surface,

but they're enough to slow a chick's fall,

and make that landing,

just a little softer.

Maybe the feathers that had

initially kept the dinosaurs warm,

now also helped them to get into the air.

And then, only a few years ago,

the mudstones of Liaoning produced

yet another extraordinary fossil.

It's been named Microraptor,

and it's clearly a small dinosaur.

But this specimen is particularly

exciting, because of its feathers.

Feathers on the forearms there.

Feathers on its hind limbs.

And even feathers right

at the end of its very long tail.

But there is something

that makes these feathers

different from any other feathers

we've seen on dinosaurs before.

They are narrower on one side

of the quill than on the other,

just like bird feathers.

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