David Attenborough's Natural History Museum Alive Page #3

is going to use its claws on me.

That dung made it clear that

these creatures are vegetarians,

so they doubtless used those claws

for ripping up plants.

But it's been discovered recently

that they used them

for something else as well.

Something that seems

rather surprising

for animals of their great bulk.

They dug burrows.

Huge excavations like this

have been found all over Patagonia

and we know they were made

by giant sloths

because scratches on the walls

of the burrows

exactly match their claws.

Such immense burrows must have been

excellent places to take refuge.

And the giant sloths

may well have had need of them

because there was a truly ferocious

predator living alongside them.

A great cat

with immense sabre-shaped teeth.

Smilodon.

For me, there is no more alarming

animal in the whole museum than this.

And its skeleton

is perfectly preserved,

because about 10,000 years ago,

it wandered into a pool

of naturally occurring tar,

oozing from the ground

in California.

In general shape,

it was somewhat like a lion,

but more muscular and much heavier

and those sabre teeth

were really sharp.

No wonder the giant sloths

needed burrows

in which to take refuge.

You might think that Smilodon

would have caught its prey

as a lion often does,

by chasing it,

leaping on it at speed

and then throttling it,

suffocating it

with a bite to the neck.

But Smilodon stalked its prey,

creeping quietly across the plains

until it got really close.

And then, it pounced!

Smilodon couldn't throttle its prey

with those huge teeth

and they were too brittle to slash.

They would shatter

if they struck bone.

Instead, the animal would have first

used its great weight

to pin down its victim.

Then it would have used its sabres

like blades

to slice open the soft flesh

of its victim's throat.

But these terrifying hunters

had a rather touching side

to their characters.

Tigers today are solitary hunters

and when one gets too old

to hunt successfully, it dies.

But skeletons of really elderly

sabre-tooths have been discovered,

which suggests that not only

did Smilodon hunt in packs,

but when members of the family

were too old to hunt for themselves,

they were allowed to take

a share of the kill.

The museum is full of creatures

that appear terrifying,

but which no doubt

if you knew them better,

would prove to have quite

a charming side to their characters.

But there is one here that would,

I think, chill everyone's blood.

This is a vertebra from the backbone

of a modern snake.

It was a python

and we know exactly how long it was

because it was measured

when it was alive.

It was 21 feet long, 7meters.

This, however, is a similar bone

from the spine of a fossil snake

and if this was 20 feet long,

how big was this?

Certainly 30 feet, 10 meter, 11 meter.

It was a monster.

But what did it live on

in those far distant times?

Maybe if I follow it,

I'll find out what it ate.

Science calls this snake Gigantophis

and it was truly immense.

Certainly big enough to swallow me.

But would it have eaten

human beings?

It might well have done if we had

both been around at the same time,

but it lived 40 million years ago

and had become extinct long before

human beings appeared on Earth.

So maybe it preyed on dinosaurs.

Well, no.

Dinosaurs are even older

than Gigantophis

and disappeared some

25 million years before it evolved.

In that case, what about mammals,

such as sheep or deer?

No - at least not modern mammals

like these.

The early mammals

were rather different

from the kinds we know today.

This is a model of

a prehistoric elephant

that was unlucky enough

to wander about the planet

at exactly the same time

as Gigantophis,

about 40 million years ago.

But how could Gigantophis

tackle one of these?

Well, he didn't use venom

to kill its prey.

We know from its massive size

that it must have been

a constrictor.

Constrictors, having seized

an animal with their jaws,

wrap their coils around their prey

and squeeze so hard

they stop their victim's heart

and it dies within a few minutes.

I wonder if he realises

that his dinner tonight

is a fibreglass model.

I'll leave him to it.

There are specimens of animals here

from every corner of the Earth.

But it was much closer to home,

on the south coast in Dorset,

that a group of amateur

Victorian fossil hunters

discovered these amazing

fossilised creatures.

But what kind of animals were they?

They clearly lived in the sea

because seashells are found

alongside them in the rocks.

They had bony paddles -

not fins, like fish -

and huge eyes,

protected by a ring of plates.

Those Victorian pioneer scientists,

led by Professor Richard Owen,

worked out that they were too old

to be mammals

and were certainly not fish.

They were reptiles.

Owen and his friends called them

ichthyosaurs - "fish lizards."

Now it's got skin and flesh on it,

you can see how remarkably similar

it is to today's dolphin.

It's got the same streamlined

silhouettes, same pointed jaws,

it's air breathing,

even gives birth to live young.

But surely an ancient ichthyosaur

couldn't be as advanced

as a modern-day dolphin?

Or could it?

Dolphins are mammals.

Ichthyosaurs, reptiles.

Very, very different groups.

They're not at all closely related

and yet, they both have

very similar body shapes.

They're a remarkable example of

what's called convergent evolution -

two groups of unrelated animals

that have evolved similar bodies

to suit the same environment.

But there ARE some differences.

Dolphins beat their tails

up and down

like their cousins, the whales.

Ichthyosaurs,

as is clear from their fossils,

had tails like fish

that beat from side to side

and dolphins only have two flippers,

whereas ichthyosaurs had four.

So is it possible that ichthyosaurs

were as fast in the water

and as agile as dolphins,

if not more so?

I wonder who would win

in a competition.

One kind of dolphin - spinners -

can leap from the surface

of the water

and spin in the air.

Maybe the ichthyosaurs

could do the same.

We know that ichthyosaurs lived

and evolved on this planet

for many millions of years more

than dolphins have done so far,

so maybe ichthyosaurs would have won

the competition after all.

Who knows?

While the ichthyosaurs

and other marine reptiles

ruled the seas

150 million years ago,

another group of reptiles

dominated the land.

They lived long before big mammals,

let alone human beings.

There are hundreds, probably

thousands of different kinds,

and they came in all shapes

and sizes.

They are perhaps the most famous

and dramatic of all

prehistoric creatures.

And they were first identified

and named here in Britain.

They were the dinosaurs.

Thousands of people come here

every day

to look at their amazing skeletons

and to imagine what they must have

looked like

and sounded like

when they were alive.

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