Original subtitles

66 million years ago,

Planet Earth was very different from today.

Back then, one of our closest ancestors might have looked

something like this little furry creature.

The rulers of the land were giant reptiles.

Dinosaurs.

That's one of the most infamous,

a carnivorous T-rex.

And just behind are the bison of their time,

a common plant-eater, Edmontosaurus.

But what happened to them all?

66 million years ago,

an asteroid hit the Earth,

and scientists think that it was this collision

that wiped out the dinosaurs.

But no-one has ever found direct evidence of that.

In fact, no-one has ever found the fossil of a dinosaur

that died within a thousand years of the impact.

However, a remarkable dig site promises to change that.

It's in the Hell Creek formation

in the American Midwest.

These badlands are rich in prehistoric remains...

..from triceratops...

..to pterosaurs.

And here, one patch of land

about the size of a football pitch

is yielding a collection of astonishing fossils.

The precise location is a closely guarded secret,

because this place may hold evidence...

..of one of the most dramatic events

in all the four-and-a-half- billion-year history

of our planet.

Right, let me get down here between you.

For ten years, a palaeontologist and his team

have been trying to find out exactly what happened here.

You're at the edge of your seat every moment,

trying to dig this stuff up.

It's like trying to defuse a nuclear weapon

while you're in a rainstorm.

He's named the site Tanis,

and believes it could be a mass graveyard

of creatures that were killed

in the catastrophic asteroid strike.

A site that could reveal not only how the last dinosaurs lived,

but how they died.

If the dig team is right, Tanis could be a place

where the remains of a long-lost world

are frozen in time.

A place that gives us, for the first time,

an unprecedented window...

..into the lives of the very last dinosaurs...

..and a minute-by-minute picture of what happened

on the day the asteroid hit.

This landscape is full of fossils

dating from the Late Cretaceous,

the period which began around 100 million years ago

and ended 66 million years ago,

when the dinosaurs vanished.

Palaeontologist Robert DePalma wants to find out more.

I think anybody who's ever liked dinosaurs

in the past, or still does,

has thought at one point or another,

"Well, what happened to them?

"Why are they not here any more?"

So many different theories are out there,

and nobody has a tight answer to that question.

Judging from fossil evidence,

this is what Hell Creek looked like in the Late Cretaceous.

There were low-lying, marshy flood plains,

intercut by river channels and covered with horsetails,

ferns and trees.

Back then, it was warm and wet here all year round.

Tanis lies in the north-eastern corner

of the Hell Creek formation.

Instead of today's dusty prairies,

there were sandy river banks.

Instead of rocky cliffs, there were forests.

And instead of the life we know today...

..well, Robert is hoping to find out more

about what that was like.

A sandbank lying between a river and a forest

would one day become what Robert now calls Tanis.

He and his team have been digging here since 2012.

So somewhere from between there

and down here is where that came from.

It's come from up above. Hey, look at this.

What? Look.

Oh, yeah, yeah, yeah. OK.

And what they found is unexpected.

Here we've got this freshwater environment

of the Hell Creek formation,

and these shocking red, green colours

coming from the shells of ammonites, a marine organism,

kind of like a coiled snail in appearance.

So we've got this marine organism that's been thrown up

into this freshwater environment,

and they do not belong here.

How they got here is a mystery.

OK...

And there's more.

I'm just going to go ahead and plane down some of this rock.

Sitting just above the ammonites

is something that many dinosaur hunters

are desperate to find.

So this orange layer right here is composed 100%

of impact-related debris that is enriched in iridium.

Iridium is an element that's rare in the Earth's crust,

but it's common in asteroids.

The layer it's in is called the K-Pg boundary.

Dear Momma...

Oh, dear. Really? Yeah.

It's made up of dust and debris from a huge asteroid impact.

Look at that. That's amazing.

Yeah, yeah, yeah, yeah, yeah. That's what we want.

OK. So it's coming from this area here.

So somewhere within that region is where these pieces are coming from.

The boundary separates the age of the dinosaurs

from the age of mammals,

so the rocks here come from about the time

that the dinosaurs became extinct.

No rattlesnakes.

What makes the site even more exciting

is the rock layer right beneath the boundary

where Robert found the ammonites.

The rock here is really not quite rocky,

as you would expect dinosaur bones and things to be encased -

you expect really, really hard rocks and jackhammers

and things like this, but it's very, very crumbly

and it just falls apart in your hands.

As well as being crumbly throughout,

this layer of rock is also around a metre thick,

which, along with other unusual features, makes

Robert think that something very strange must have happened here.

Maybe a flood or a mud flow,

burying anything within it in an instant.

Oh, there's a beautiful... Look at that one - beautiful.

This could mean that anything he finds in this layer

would have been quickly entombed,

like the bodies in the volcanic ash of Pompeii.

Robert knows from the geology

that anything he finds at Tanis will be tantalisingly close

to the end of the age of the dinosaurs

and could be so well preserved

that it could reveal new evidence

that will bring this time period to life

in a way no-one has ever done before.

Robert digs at Tanis each summer,

the only time the weather allows him to do so.

Come on down, check out this lens over here.

In order to understand how the impact affected life on Earth,

you really need to get a very clear picture

of what the world was like right before.

That is a critical part of the story.

Palaeontologists Dr David Burnham

and Loren Gurche have been digging with Robert for years.

Oh, wow!

See...see the brown? Yep.

That might be a tubercle right there.

And it seems today is their lucky day.

Oh, my God! Look at that! Look at that.

Look, the scales are preserved!

Holy crap! Like doing a freaking dissection.

Oh, my God. Biology of Tanis.

Oh, the scale...

Look, look - the wrinkles continue down that way.

Mine's all nice and wet so far.

The scales are getting smaller in that direction.

How big are they there?

I got a...I got one with the projection over here.

What? Oh!

Yeah. Oh.

Yeah, there's the protuberance right there.

I've only seen that on one other specimen, in life. Yep.

This is the closest thing to getting to touch

a living, breathing dinosaur.

It is.

They found something extraordinary.

It is so exceedingly rare -

a piece of triceratops skin in the Hell Creek formation.

It may look like an impression in the rock,

but this is skin that has been fossilised

and, over millions of years, has turned to stone.

Triceratops bones are relatively common finds in Hell Creek,

but skin in such condition as this is very rare indeed.

The size and the patterning of the scales,

together with the age and location of the rocks

where it was found, strongly suggests

that this is from a triceratops.

The brown colour contains traces of organic material.

So it might even be possible from this

to work out which pigments were in it.

Finding and studying

such well-preserved fossils as this

helps palaeontologists build

a much more detailed picture of how these creatures lived.

Combining this information

with insights from scientists around the world

makes it possible to speculate

about what life in the Late Cretaceous

might have been like.

We know from bones

that adult triceratops could reach nine metres in length

and three metres in height.

Marks on the fossil also show us

that this one was badly scarred.

Triceratops were plant-eaters.

Other fossils tell us that they had sharp beaks

and hundreds of teeth that enabled them to shred tough plants

such as these cycads.

Almost all adult triceratops fossils,

including Robert's, have been found on their own.

So it's possible that the adults were solitary,

like modern-day male rhinos.

So they were probably territorial,

chasing rivals away.

And perhaps marking their territories.

If you weigh more than an African elephant,

there's not much that can bother you...

..except perhaps a little mammal.

Robert found these jawbones

in the fossilised burrow at Tanis.

The shape of this tiny bone and tooth

means it's most likely come from what's known

as a pediomyid, an early mammal

and a type of marsupial.

Robert also discovered fossilised nuts and seeds

in the burrow.

So we have an idea about what it might have eaten.

Robert's finds are adding

to our knowledge of the complex world

at the very end of the Late Cretaceous.

And it's not just the fossilised creatures.

If you walk on damp sand,

you'll leave a trace behind.

A footprint.

The same was true 66 million years ago.

And very, very occasionally, such traces were preserved.

And that's exactly what happened here at Tanis.

You know, we won't foil a backside.

Right, we'll just put... Put plaster right on.

That way you've got...

Robert has discovered a number of footprints.

Yeah. Let's see.

Looks like a good print. Yeah.

Their shape gives him a clue

as to what might have made them.

If he's right,

they were made by a winged creature,

that might well have liked a small mammal...

..for lunch.

The footprints are long and narrow

with four toe prints.

Two are slightly longer than the others,

and that suggests they were made by...

..a pterosaur.

Pterosaurs are not dinosaurs, but flying reptiles

on a different branch of the evolutionary tree.

Male pterosaurs usually had crests,

while females didn't.

So crests may have been used in courtship displays.

And we have an indication of where females laid their eggs,

because evidence suggests one pterosaur laid hers

in the soft, sandy banks of the river at Tanis.

And this is a fossilised egg

of a pterosaur that Robert found there.

The only one ever discovered in North America.

If you look at it with the naked eye,

all you see is a jumble of lines.

But if you examine it with the latest technology,

you can find out a wealth of information,

from the chemistry of the bones

to the composition of the shell.

And that, in turn, can tell us a lot about

how these incredible creatures lived.

Robert has been given access

to the Diamond Light Source synchrotron in Oxfordshire.

It's a very powerful research tool

that acts like a giant microscope.

By accelerating electrons in this huge ring,

the synchrotron creates beams of light

many times brighter than the sun.

Robert and paleobiologist Dr Victoria Egerton

now want to turn that beam onto the egg fossil

to discover more about its chemical make-up.

We're pretty much lined up on the skeleton,

but we might have to move the stage a little bit

to get to the right part. Sure.

Meanwhile, Robert can reveal the creature inside.

And this?

Who made this wonderful thing?

I got replicas of the bones from inside that egg

and I restored the remainder

and put together

what the skeleton would've looked like when it hatched.

That's how big the creature would've been

outside the egg, if it had hatched.

So this is the baby. How big was it going to grow?

These very long neck vertebrae here

are what really gave part of the story away to us,

because those long bones match very, very closely

with the azhdarchid pterosaurs.

That is the giant pterosaurs.

Oh, they were the whoppers, weren't they?

I mean, what, 25 feet?

Wingspan? Some of them.

This probably had a wingspan, maybe 15 feet, five metres.

Well, it looks as though it could take off, really.

It's easy to picture something like that

just hatching out of the egg and fluttering out,

almost like a little bat.

They've scanned the egg, here and in America.

Victoria has the results.

So what have you learned from the synchrotron image?

What we have here is a chemical map

of calcium directly within the bones of this animal.

That tells us that these bones were already hardened.

So it might be ready to fly not long after it hatches.

OK. Can you see any sign of the shell,

and what sort of shell was it?

We can. What I can show you...

Ah!

..is we can see the rim of the egg in sulphur.

Does that tell you whether it was a hard shell or a soft shell?

We have been looking at this.

We can see folding occurring, and this unusual undulation.

If it were a hard egg,

we would expect splintered bits and broken bits,

just like a chicken egg.

This helped to tell us that it was soft.

So it was perhaps like a turtle?

Absolutely.

That's not the case, is it, with dinosaurs?

Many dinosaurs laid hard-shelled eggs. Yes.

So this is a new discovery about azhdarchid pterosaurs?

Absolutely. This is something

that we are confirming for the first time.

Huh!

That flying pterosaurs had eggs like turtles.

Yes.

Much more reptilianlike than birdlike.

And that can potentially tell us more

about the environment in which these eggs were laid.

How interesting. Yeah.

Creatures that lay soft eggs tend to bury them

in order to protect them.

So female pterosaurs probably looked for

places like Tanis to lay their eggs...

..because the sandy soil here is just soft enough

for the hatchling to dig itself out.

Now the pterosaur just has to make sure

that the hole...

..is perfect.

Success!

But it's not over yet.

Pterosaurs had two ovaries,

and they laid their eggs in pairs.

Here on the sandbank,

sandwiched between the river and these glorious trees,

life at Tanis seemed to be thriving.

Whoops!

Never a dull moment.

But all that was about to change.

The chain of events that led to the extinction of the dinosaurs

began in the distant past, deep in space.

Most scientists think it all started in a ring of dust,

rocks, and debris known as the asteroid belt.

It's usually an uneventful place.

But it's thought that many, many millions of years ago,

a rock was bumped into a new orbit...

..and diverted onto a collision course with Planet Earth.

Robert is building a vivid picture

of Late Cretaceous life at Tanis.

And the team have found some more well-preserved footprints.

So these are animals that were actually walking in the water?

These guys would've been essentially on

a mushy river bank going down

to drink at some point.

You know, animals tend to congregate around the rivers.

This print is 30 centimetres long.

So I think this is from a type of dinosaur

that we call a duck-billed dinosaur.

And they would've been very common in the Cretaceous.

They ate the plants in the area

and they got very large - 30 feet long.

And there are more.

This track, you see all the toes are very well preserved.

You even see a nail print at the tips of the toes.

So the little toenails dug into the mud.

I love this one.

This is Robert's prized footprint.

It has three toes,

and it's longer than it is wide.

So it's very likely to be a carnivorous dinosaur.

It's so well preserved that you can see

the mark left by its sharp claw there.

Hell Creek is well known

for one carnivore in particular - T-rex.

This footprint is too small for an adult T-rex,

but it's possible that it was made by a young one.

Robert also found this at Tanis -

the crown of a tooth.

Its shape and its serrated edge

are indications that it comes

from an adult T-rex.

Bite marks found on T-rex bones

show that they ate other T-rexes.

And a youngster would make an easy catch.

But not this time.

Very few footprints are preserved as fossils

in Hell Creek.

So if you find several in one place,

as Robert has done,

it's a reasonable assumption

that there would've been many more nearby.

And that supports the idea

that dinosaurs and pterosaurs were thriving at Tanis

shortly before the impact.

And if they were thriving...

..they must have been reproducing.

Fossils from dinosaurs similar to T-rex

show they may have laid around 20 eggs

in a circular nest.

It's possible that, like crocodiles,

they partly covered their eggs to keep them warm.

For one T-rex, a misfortune.

But for all dinosaurs...

..a disaster was looming.

Deep in space, the asteroid was approaching.

Its journey would take it through the orbit

of our neighbouring planet, Mars.

Had the two collided,

a catastrophe on Earth would've been avoided.

But it was not to be...

..and Earth's fate was sealed.

As Robert's dig continues,

his vision of what happened at Tanis

is finally starting to come together.

It seems the sandbank was full of life.

T-rex, triceratops,

little mammals,

alongside the footprints of other dinosaurs and pterosaurs,

all in a very small area.

You see the scales?

I do. Oh, my God.

That excites me just looking at it!

Then Robert finds something truly remarkable.

See the cracks already forming? Look at that.

So we're going to have to really monitor that before we glue it.

Cos this is getting vulnerable now.

An almost complete creature.

To get this block out, we're freezing it.

Robert is about to attempt something tricky.

Steady... Let's go.

To get the fossil out in one piece, they're trying

to freeze it using liquid nitrogen

at almost 200 degrees below zero.

Watch your footing.

Loren, I'm worried about brittleness here.

Get that hammer. Give this a couple whacks with the hammer.

OK. Move over five centimetres. Good.

It's cracked loose. Yep. OK. It's loose.

So we have to get this out in one piece.

One, two, three.

Yeehaw!

Total success. Total success.

This is a technique used in archaeology

for digging up human remains.

We've got enough time to work with the fossil

and not damage it.

And I couldn't be happier.

And the creature Robert found?

A turtle.

This is the fossil now it's been cleaned up.

It's lying on its side.

Here's the outline of its shell.

The shape of the shell and the scalloped edges here

tell us that this was a baenid turtle.

Robert's baenid turtle looks very similar

to modern cooter turtles

and lived in the same sort of freshwater environment.

For a turtle, Tanis would've been ideal.

Warm, shallow water.

Plenty to eat.

And lots of safe places in which to warm up

in the Late Cretaceous sunshine.

The turtle fossil Robert found is almost complete.

This is the underside,

and this brown material up here is fossilised wood.

It's the end of a stick that passes right through its body

and comes out just here.

So the evidence points towards

this turtle having been impaled.

A violent end to one of the many creatures found

in the crumbly rock layer at Tanis.

When I look at the animals

and plants preserved in the sediments of Tanis

and the footprints beneath it,

I see a picture of a vibrant ecosystem,

many different dinosaurs, and a thriving, thriving place.

After ten years of digging,

there is now enough evidence to piece together

much of the story of Tanis

and the creatures which lived here.

Robert has found so many fossils, it looks as if,

even at the very end of the Late Cretaceous,

Tanis was bursting with life.

Full of the giant reptiles that had dominated the planet

for more than 150 million years.

It's impossible to know how much longer

their reign would've continued...

..because all this was about to end.

The asteroid hit...

..in what is now the Yucatan peninsula in Mexico.

It's called the Chicxulub asteroid

after the town nearest to the centre of its crater.

Any living thing within 900 miles of the impact...

..was destroyed by the blast.

But what effect did the impact have on Tanis,

nearly 2,000 miles away?

To find out,

Robert is looking for clues that might link Tanis

to the actual day the asteroid hit.

We've got some wood,

and pressed up against this and all intertangled,

we've got the carcasses of fish.

OK.

That's a beautifully preserved tail,

so that fish is going to be absolutely gorgeous.

So part of the detail work that we're doing right now

is going in and checking out

all the individual elements in this mass death layer.

Some of the evidence he's found so far

has been hidden inside the fish themselves.

In more ways than one, it literally is an operation of a Cretaceous

fish, so we're performing surgery on this thing.

Robert needs to open this fish's skull.

And very carefully, we want to separate this

from the rest of the fish.

OK.

Here we go.

Opening up the fish.

Got a nice ant that made a home in there.

And beautiful, look at that.

OK, here we have the gill bars of the fish.

Those are the bars that hold the filaments of the gills.

And between the gill bars,

all of these clusters of round objects,

those are the ejecta spherules.

Ejecta spherules are tiny balls that were once molten rock.

They could be evidence of what Robert suspects -

that creatures here died

on the day of the asteroid strike.

Those ejecta spherules last saw the light of day

when they were flying through the air 66 billion years ago.

After a large asteroid impact,

a mix of vaporised and molten rock

is propelled into space.

There, it cools,

solidifying into tiny glass droplets.

Some carry on deeper into space.

But most are pulled back to Earth by gravity.

After a major asteroid hit,

trillions of ejecta spherules would fall from the sky.

Then, over millions of years,

pressure and chemical reactions in the ground

would turn most of them to clay.

They'd look something like this.

So finding spherules in the gills of a fish,

as Robert has done at Tanis,

suggests the fish sucked them in

while the spherules were still falling.

So these creatures could have died

at the time of an asteroid impact.

Once Robert begins to look for ejecta spherules,

he finds more and more,

and realises the thick, crumbly layer of rock at Tanis

is full of them.

I mean, this stuff is go... Oh, my God, look at that one.

These things are just gorgeous.

Ejecta spherules like this

give us a fingerprint of where they came from.

If these spherules were connected

to the Chicxulub impact,

then the whole crumbly layer could be full of evidence

of what happened on the day the asteroid hit.

That's a good one.

Oh, is that a droplet right there?

To see if that's the case,

Robert needs to find a spherule that hasn't turned to clay.

Oh, my God, that's a beautiful droplet.

OK.

The small pieces of orange material

that Robert and Loren are digging up

may be able to help.

They're amber.

If there was anything flying through the air at that time,

this is where it's going to get caught.

The amber they're collecting was once sticky resin

oozing out of a Late Cretaceous tree trunk.

It's a way for the tree to protect itself,

like a scab forming on a cut.

Anything covered by the resin would be frozen

in an amber time capsule.

If they find a spherule preserved in amber,

it could be analysed

to see if it comes from the Chicxulub asteroid impact.

So during this batch,

we were incredibly lucky that we came across

two completely unaltered spherules.

This spherule could be something amazing.

Evidence preserved well enough to analyse for chemical clues.

If so,

it could link Tanis directly with the Chicxulub impact

and the last day of the dinosaurs.

To investigate, Robert is joined

at the Diamond Light Source

by Professor of Natural History Phil Manning,

of the University of Manchester.

They've already run initial tests

on the spherules in America.

What have you found out so far?

These little glass spherules, these globs

of molten material from the impact site

have a chemical signal that ties it with where they came from.

Cos when an asteroid hits,

it melts the ground that it hits,

but also that glass has

a little bit of contamination from the asteroid itself.

And that gives you a unique geochemical fingerprint.

We can see once we've scanned it,

and looking at spherules from other sites in North Dakota,

we can get a baseline

for what the ejecta should look like when it's related to

the Chicxulub crater.

And you can see each element here

and the ratios of those elements.

And when we look at Tanis, it's a match.

I mean, it perfectly overlays.

So I think this is powerful evidence

supporting that Tanis and Chicxulub are linked.

And what do these findings mean

for the rest of the fossils that you're finding in Tanis?

This data is key for the entire site,

because once you have that link

and you know what impact affected Tanis,

then you essentially know that every object in that site,

all the animals and the plants and everything buried

in those sediments,

are linked to the last day of the Cretaceous.

And the synchrotron here in the UK

reveals something even more remarkable.

So this is showing a beautiful synchrotron scan

of the half of one spherule.

The glass is a good geochemical fingerprint,

and we've got calcium, some iron,

we've got strontium,

but when we look at the entire thing,

we see something quite unexpected.

That's your entire spherule.

What's this?

In this, we've got a little bit of a nugget.

There was a little particle right there.

So we scan it.

And that's a lot of iron in there.

Over here, we've got chromium, a big peak in chromium.

Over here, we've got a big peak in nickel.

And the abundances of iron, nickel and chromium,

all together,

that matches what you expect to see in a meteoric body.

That does not match what you would normally have down here.

So this is extraterrestrial material?

If you were to sort of grind up

and stuff into a spherule a piece of meteorite,

that's what it's going to look like.

This could be a piece of the Chicxulub asteroid.

A piece of the bullet that killed the dinosaurs.

No!

Robert could have found

a fragment of the asteroid itself in Tanis,

physical evidence linking this site to the Chicxulub impact.

But Tanis is almost 2,000 miles away

from where the asteroid hit.

So exactly how did it cause the creatures' deaths?

To answer that question,

Robert is searching in the mass death layer.

Right here, we've got this intertangled mass of fish.

There's one fish here, another sturgeon goes this way,

underneath the body of a paddlefish.

There's another sturgeon that goes this way,

underneath this log, and continues out the other side.

And his head hit that log

and has deflected downward at a 90-degree angle.

Robert uncovered a tangled mass of fossilised creatures and logs

surrounded by spherules

and crushed together in what's known as a logjam.

He has a theory that the creatures were swept

to their death in some kind of turbulent surge of water

and quickly entombed in sediment,

which is why they're so well preserved.

But what could have caused the wave?

One theory is a tsunami.

The asteroid hit at sea.

Recent studies show

it may have caused a wave almost a mile high.

The height of the wave would've gradually reduced

as it spread across the oceans.

In the Late Cretaceous,

North America was divided by a narrow sea

that's been called the Western Interior Seaway.

The tsunami could have travelled up this,

towards Tanis.

But there's a big question about the tsunami idea.

The timing.

Oh, which fish is that?

That's a new... It's a new contact. New one. Yeah.

If a tsunami killed the fish,

it would have to have hit

while ejecta spherules were falling...

..because spherules were found in the fish's gills.

So how long after impact did the spherules arrive at Tanis?

Pretend this ball of foil is a piece of ejecta

coming out of the crater. It would then go on an arc path,

ballistic trajectory, out of the crater

and to wherever it lands - in this case, Tanis.

If we know the distance between myself

and the landing site, and if we know the size of that ball,

we can accurately calculate how long it would take to get there.

The result is surprising.

Robert and his team calculated

that these ejecta spherules landed at Tanis

between 13 minutes and two hours after the impact.

If a wave killed the fish,

it must also have reached Tanis within two hours.

Data from recent tsunamis show

even a powerful one would take much longer than that

to travel almost 2,000 miles from the impact site

to Tanis.

So if it wasn't a tsunami,

what could have caused a surge of water at Tanis?

Professor Stein Bondevik is an expert in tsunamis.

The fjords in Norway are very special.

We have tall mountains surrounding bodies of water.

So the water is usually very calm.

In 2011, something very strange happened.

The water in the fjord began to move violently.

The height of the water increased by one and a half metre,

like a maelstrom with the turbulent water.

Someone said that the fjord was boiling.

News started to roll in -

there'd been an earthquake 5,000 miles away in Japan.

A journalist from the local newspaper called me,

and he said that people were observing waves

here, in the fjords.

I got a video clip of the waves.

I saw immediately that they looked like a tsunami wave.

So later in the afternoon,

you can see that the fjord is perfectly calm.

But at the beach here,

you could see that the water is sloshing back and forth,

and no-one had ever seen anything like it.

And some people got very upset and afraid.

A magnitude nine earthquake had devastated the northeast of Japan,

around Fukushima.

But how did that affect a fjord so far away?

So no-one in Norway could feel the earthquake,

but I could see that the times matched

the arrival of the waves here, in the fjord.

Eventually, Stein and his team realised

that this might have something to do with seismic waves -

shock waves that pass quickly through the Earth

during an earthquake.

So it took only 12 minutes before the first signal

of the earthquake in Japan reached all the way here,

to western Norway.

So it was the seismic waves

that caused the normally calm water in the fjord

to slosh turbulently back and forth.

Just thinking of that, scientifically, it's fantastic.

Could something similar have happened in Tanis?

A large weather front's coming through the northwest...

Trying to find out

is geophysicist professor Mark Richards,

who's been studying the site at Tanis for several years.

He's working with Robert to discover

what could have caused a surge of water here.

A tsunami can't get here in less than minimum 12 hours.

But seismic waves travelling from the Yucatan impact site

to North Dakota can arrive here fairly quickly.

In the Late Cretaceous, the Western Interior Seaway

that divided North America could have been connected to Tanis

through a system of rivers.

If you have a very large body of water,

like the Western Interior Seaway,

and you can shake it back and forth,

you can generate a large water wave

coming up this river at Tanis.

So seismic waves from the impact could have caused

surges of water in the Tanis river system.

The seismic waves get here quickly enough,

coming up the Tanis river,

inundating this area, arriving at the same time

these spherules are still falling out of the air.

The mystery of the wave

and the thick layer of crumbly rock has been solved.

Seismic waves travelling through the Earth

could have caused powerful surges of water at Tanis...

..possibly carrying mud and marine creatures,

like ammonites, from the Western Interior Seaway...

..dumping them on the Tanis sandbank and burying everything

at the same time as spherules fell.

Over millions of years,

the mud would turn into the layer of crumbly rock.

And that's the beauty of Tanis.

What you're seeing is a deposit

that is literally recording the last, say,

45 minutes to an hour and a half of the Cretaceous.

If the extinction of the dinosaurs was a crime,

the detective solving it would have plenty of evidence.

They would see that the asteroid was

in the right place at the right time.

They would see that no dinosaurs survived

after the hit.

They would have a piece of the murder weapon -

a fragment of the asteroid.

But they would be missing one very important thing -

a body.

No-one has ever found the fossil of a dinosaur

that was killed by the effects of the asteroid impact.

But Robert did find part of a triceratops

in the crumbly layer at Tanis.

So could that be the remains

of a dinosaur that died on that day?

I'm still dubious about the horn.

I kind of want to keep the horn in the jacket.

I think if you took it off,

at least take this section off,

to see what's going on under here.

Yeah?

To find out, the team needs to establish cause of death,

which can be difficult when you only have a piece of skin

and a horn to go on.

This is the horn after they've cleaned it up.

The team is particularly interested in these lines here.

And they found that the fractures go

right through the horn.

So rather than dying as a result of the impact,

they wondered whether it had been killed in a fight.

But when they looked at the fractures in more detail,

they found signs of new bone growth here.

An indication that the bone had started to heal.

So it looked as though the triceratops survived

the event that broke its horn.

Could this triceratops have survived

until the day of the impact?

The team found evidence, including sagging in the skin,

which suggested that there was decay underneath.

That means its body had started to rot

before it was entombed and preserved by the surge.

So it seems that this dinosaur didn't die as a result

of the asteroid impact.

Perhaps, in the months before the impact,

the broken horn put the triceratops

at a disadvantage over its rivals.

And that might have led to starvation.

Robert has still not found direct evidence

of a dinosaur that was killed by the asteroid.

We've got all these bones in the ground right now.

But the one thing that we would just dream

of finding is that one dinosaur

that died on the day of the impact.

And the weather isn't helping his search.

That therapod print is toasted.

Yeah, it was in a low corner.

Look, it's full mud. It's full of mud and water.

The problem is it's wet, look.

See... If we're not careful, we're going to lose the print.

And that's the biggest theropod print we've got.

I see some areas that could use glue right now, too.

The team is racing to excavate the footprints,

along with dozens of fish fossils

tangled together in a logjam, before storms wash them away.

We're up against the clock here.

This stuff that could be exposed right now

is going to get ruined by the rain.

But then, Robert comes across something

that looks very unusual.

That's going there.

What is going on right there?

Are we sure this isn't crocodilian?

That's not crocodilian. No.

Right, let me try this piece right here.

I'll go in from the top and then twist up,

and it separates right on that line.

Oh, that's skin right there.

That's actually scaly skin. Oh, my God.

No, no, no, no, no. Look, look, look.

Look at that pattern right there.

Have you ever seen elongated scales like that before, Dave?

That's insane. Scuttelates - in birds.

Just careful.

Oh, my God. It's changing again.

It's changing again. Oh, my God.

We're seeing it for the first time in 66 million years.

I think we've got ourselves a dinosaur.

A dinosaur fossil!

And, unlike the triceratops,

this is located in the logjam, the mass death layer,

surrounded by the fish with spherules in their gills.

This is the most incredible thing that we could possibly imagine here.

The best-case scenario.

We're excavating this mass death layer of fish

from the surge sent up by the impact,

and we've got dinosaur remains.

The one thing that we would always want to find at this site,

and here we've got it.

This is unreal. I-I-I cannot process this in my brain.

No, I am absolutely blown away by this.

Just my heart is literally pumping out of my chest

wondering what is behind there,

just a couple of centimetres back in the outcrop.

What is waiting for us back there?

Get it out...

This is...

The team keeps digging.

The scales get big again over on this side.

So this could be a ribcage,

it could be laying against ribs that are curved.

There's something here.

That's hard. A bit more bone.

That's bone right next to the skin.

Yeah, that's an articular surface right there,

so this is either a hip or a shoulder element.

After hours of painstaking work...

And we can go from the thigh of the animal.

There's the knee.

And then you've got the little calf muscles

of the dinosaur, they're bulging out,

and you go down to the anklebones,

and these are the toes of the feet.

We have got nails at the tips of the toes.

It's a beautifully preserved leg,

all articulated, covered with skin.

The complete leg of a dinosaur.

In my wildest dreams,

I never expected to find a dinosaur leg in this deposit.

Yeah. I mean, and then it's got skin and tissue.

It does look just like a drumstick.

It looks like a Thanksgiving turkey,

just laid out in the ground.

And this weird scale pattern on the thigh of the animal,

which we've never seen in a dinosaur before.

Well, thescelosaurs don't have any form of defence,

so they have to have camouflage or something.

That's a good point.

So this could have been some sort of a camouflage marking. Yeah.

Robert thinks he has found the body in question -

a dinosaur that might itself have witnessed

the cataclysmic impact.

Dinosaur fossils are not known

from the last years of the Cretaceous.

And it was unclear whether they were already extinct

or in decline or what was going on.

So they were just sort of absent.

And this answers that question.

Were dinosaurs still there then?

Well, yes - this one likely died in that surge.

For such big claims, Robert needs verification.

He's brought the dinosaur leg to London

to get a second opinion...

And then here are the pads of the toes.

We see all those beautiful scales lined up.

..from Professor Paul Barrett,

an expert in ornithischian dinosaurs

from the Natural History Museum.

So what do you think this might be?

When we look at the leg, it has claws,

like the claws we see in small, agile, bipedal, running dinosaurs

that are plant-eaters.

We can rule out things like triceratops,

partly just because it's not big and stocky.

And the proportions of those legs are also different

from some of the other plant-eaters we see,

in that they have this rather long ankle

and shin, compared with its thighbone.

So as we narrow those possibilities down,

what we're left with, probably,

is an animal called a thescelosaur.

Thescelosaurs lived next to rivers

where there was plenty of rich vegetation to feed on.

They had leaf-shaped teeth,

common amongst herbivores,

and claws on their short front limbs -

excellent for digging.

But how did Robert's thescelosaur die?

Could it have been killed by another dinosaur?

It's a possibility.

This is a relatively agile animal.

And that turn of speed would've been

its primary defence against the large predators living alongside it.

So, to escape a hungry T-rex,

a thescelosaur's first line of defence...

..would've been to run.

But it may have had another defensive trick.

Living next to rivers,

it's possible thescelosaurs were able to swim.

It doesn't seem to me like there is any evidence

that this animal was predated -

none of the obvious tooth marks

or leftover bits of carnivore teeth

to suggest it's been eaten.

So how do you think it died?

It didn't have any particularly nasty diseases when it died,

as we can see that the bones look OK.

So this is an animal that was probably living

and healthy at the time that this happened to it.

Could this be a victim of the meteor strike?

I think it's entirely possible.

This is actually a shoulder bone,

and this bone in a living animal

would actually be way over here.

And similarly, this little bone here

would've been from about maybe a third of the way

along the tail, maybe halfway down.

So somehow these two bones have been telescoped together.

So maybe this animal's been tumbled around.

We've ruled out a lot of other possible

causes of death for this animal.

So it could well be that this is an animal

that was there, being tumbled around

in its death throes, in that river,

as a result of the asteroid impact.

Well, it is exactly analogous

to those human bodies found in Pompeii.

It's very similar in terms of you get that quick entombment.

Yes. And it's almost as evocative.

That's absolutely true.

You've got literally the blink of an eye

at the end of the Cretaceous,

snapped up into history, and there it is,

ready to be dug up. Wow.

After years of investigation,

Robert has found out a great deal

about the creatures which lived at Tanis,

and he knows that many of them were alive on that fateful day

when the asteroid devastated our planet.

But how exactly did they die?

Robert's finds now allow us to tell the story of that day

and finally answer that question.

One of the most important days in Earth's history

probably started much like any other late spring morning.

We know the season because Robert found fossils of young fish that

died at the size they reach at that time of year.

This agrees with evidence already found

by other scientists.

Perhaps this day, that would end with so much death,

began with something different.

A new life.

No-one can be certain of the exact timings of the day

when the asteroid collided with our planet.

But it's estimated that within just 40 minutes of the impact,

the consequences for the creatures of Tanis

would have been profound.

Based on Robert's finds

and the latest evidence from other scientists,

this is how the catastrophe might have unfolded.

The asteroid is around seven miles across,

bigger than Mount Everest...

..and travelling at close to 45,000mph.

The impact causes an explosion

bigger than a billion Hiroshima atomic bombs.

At Tanis, almost 2,000 miles away...

..it's completely silent.

But at the impact site...

..the asteroid vaporises.

More than three trillion tonnes of rock

are ejected into space

in a blast of super-heated violence.

Winds higher than 600mph.

A colossal earthquake, followed by a ring of massive tsunamis.

All the while, the creatures at Tanis

go about their business...

..just like any other day.

The evidence suggests that baby pterosaurs

emerge from the egg ready to fend for themselves.

And that includes...

..flying?

Well, almost.

Elsewhere, as the devastation spreads out across North America

towards Tanis...

..dinosaurs and creatures of all shapes and sizes

are obliterated by the blast.

At Tanis, for a few more precious minutes,

life carries on as usual.

But the clock is ticking.

The blast from the impact never reaches Tanis,

but seismic shock waves do.

They are far more powerful

than any earthquake ever recorded.

The thescelosaur might head for a place of safety...

..but seismic waves are now slowly shaking

the whole region, causing water to slosh and churn.

At Tanis, strange currents in the river

give a hint of what is still to come.

Next, it begins to rain.

Ejecta spherules are falling back to Earth.

As the spherules begin their fall...

..friction heats them until they're red hot.

Then the heat transfers to the air.

Temperatures rise with every second.

As the heat builds, the creatures of Tanis

are fighting for their lives.

And then, as seismic waves

continue to slowly rock the whole region...

..a violent surge wave ten metres high

rushes up the Tanis river.

Surviving the turbulence of the surge

is a challenge even for the best swimmers.

Then, the powerful rocking of the river system

slowly begins to draw the water back the way it came.

Swimming may have saved

the thescelosaur in the past,

but not this time.

A large, robust animal like a T-rex

might have survived the surge.

As might a hard-shelled reptile.

But there is much more to come.

As billions of tonnes of superheated spherules continue to fall,

the atmosphere gets even hotter...

..igniting dead leaves and sparking wildfires.

Earthquakes,

fire...

..devastation.

Little would survive for long,

on land..

..or in the air.

As the air reaches the temperature of an industrial oven...

..those that live deep underground

may have a better chance.

As the slow sloshing of the river system continues...

..another powerful surge hits.

There is no escaping the destruction.

For many of the creatures of Tanis,

their stories end underwater.

In less than two hours, the world has changed forever.

The mud the surge waves leave behind

will gradually turn into the thick layer of crumbly rock

entombing the creatures which died here...

..until 66 million years later,

when they're finally unearthed.

Robert's finds have helped us understand in remarkable detail

what happened at Tanis

in the minutes after the asteroid impact.

But what about the rest of the world?

The impact triggered catastrophic events

such as earthquakes all over the planet.

And as spherules continued to fall...

..wildfires may have sprung up around the globe.

As that horrific day drew to a close,

many of the world's dinosaurs were already dead.

Research shows that the angle at which the asteroid hit

and the sulphur-rich rocks at the impact site

amplified the devastation.

Billions of tonnes of sulphur

were ejected into the atmosphere,

blocking the sunlight.

Without light, most plants died, and food became scarce.

As the weeks and months passed,

any dinosaur left alive would've died of hunger.

In the oceans, it was the same.

Nearly all of the world's plankton disappeared,

leading to the starvation of most marine creatures.

It's thought that the nuclear winter that followed

caused a global temperature drop

of at least 25 degrees centigrade.

The fossil record tells us that this huge change in climate

marked the disappearance of three quarters of all species,

including the dinosaurs.

The planet was in semi-darkness for around a decade,

as dust and soot slowly fell to Earth.

But then came something wonderful.

A new beginning.

Once the dust cleared from the atmosphere

and the sunlight returned...

..plant life was gradually restored,

led by ferns,

the spores of which had lain dormant deep underground,

and the world began to turn green once more.

But what about the animals?

Back at Tanis, Robert has unearthed something

that could have helped save some of the creatures

from the devastating fires.

We saw a little thing poking out,

so we kind of followed it back.

And I'm so glad that we did,

because what we have here is a fossil burrow

from an animal 66 million years ago.

The only animals that would've been around back then

that would likely build a burrow like this

would be the small mammals, roughly ferret-sized,

and also some reptiles.

If it is from a mammal, this is sort of a window

into the lifestyle of some of our oldest ancestors out here.

This guy would've burrowed sideways,

right into the river bank.

We actually have some scratch marks on there

from the interior when they were digging it,

going back, and he would've lived back here

and sought shelter from the dinosaurs

cos they just did not want to get eaten.

Burrows are part of the reason

that mammals survived the great extinction.

During the nuclear winter,

a burrow would've provided warmth,

protection, and a place to store food.

Mammals that survived were resourceful omnivores,

and insects would've been a plentiful source of food.

And they had another advantage - their size.

If conditions are right, many animal species get larger

as they evolve over millions of years.

Take T-rex as an example.

This is a cast of the lower jaw

of a predecessor, called gorgosaurus,

which lived 72 million years ago.

Whereas this is the cast of the lower jaw of a T-rex,

which lived five million years later.

Look at the difference in size.

But the bigger the creature,

the more energy they need to stay alive.

So when catastrophe strikes and food is scarce,

the largest tend to die out,

whilst the smallest often survive.

That's one of the reasons

why many of the smaller mammals

lived through the great darkness.

And they weren't alone.

Robert's fossil turtle may have been unlucky,

but many others survived.

As did crocodiles,

snakes,

and many fish species.

And as for the dinosaurs,

did the impact really kill them all?

Well, this beautiful fossilised feather

isn't from a bird,

but from a predatory dinosaur.

So we have to be careful

when we say that dinosaurs are extinct,

because what we call birds originally evolved

from the smallest feathered dinosaurs.

So to be correct, we should say

all non-avian dinosaurs are extinct.

Robert's finds have given us

a better idea than ever before...

..about what happened on the day that led to the extinction...

..of the largest beasts ever to walk the Earth.

Dinosaurs were perhaps

some of nature's most extraordinary creatures,

dominating the planet for over 150 million years

before they became extinct.

But extinction comes in different forms,

and many of the amazing creatures

and plants alive today are also threatened.

It's possible that humanity is having

as big an impact on the world

as the asteroid that ended the age of the dinosaurs.

As human beings, we are unique in our ability

to learn from the distant past.

Now we must use that ability wisely and do our very best

to protect the millions of species

for whom, alongside us, this planet is home.

Who are the real-world Illuminati ? Find out @ saveanilluminati.com