All language subtitles for Dinosaurs - the Final Day with David Attenborough (2022) WEBRip 720p YTS.MX - YIFY

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.

RUMBLING GROWL

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...

ROARS

..from triceratops...

SQUAWKS

..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...

SHRIEKS

..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...

DEEP RUMBLING CALLS

TRILLING

..well, Robert is hoping
to find out more

about what that was like.

COOING

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.

RUMBLING

Marks on the fossil also show us

that this one was badly scarred.

RUMBLING GROWL

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.

DISTANT TRUMPETING

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...

SQUEAKING

..except perhaps a little mammal.

GROWLS

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.

DISTANT TRUMPETING

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.

SQUAWKS

Pterosaurs are not dinosaurs,
but flying reptiles

on a different branch
of the evolutionary tree.

SCREECHING

Male pterosaurs
usually had crests,

while females didn't.

So crests may have been
used in courtship displays.

SHRIEKS

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.

SQUAWKS

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.

SNIFFING

Now the pterosaur
just has to make sure

that the hole...

..is perfect.

SQUAWKS

WARBLING

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.

GASPS

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.

RUMBLING GROWL

DEEP RUMBLING GROWL

GROWLS

Bite marks found on T-rex bones

show that they ate other T-rexes.

And a youngster
would make an easy catch.

SNEEZES

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.

GROWLING

And if they were thriving...

SQUAWKING

..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.

SNEEZES

For one T-rex, a misfortune.

But for all dinosaurs...

ROARS

..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.

BLOWS

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.

VARIOUS ANIMAL CALLS

Full of the giant reptiles
that had dominated the planet

for more than 150 million years.

BARKING

It's impossible to know
how much longer

their reign would've continued...

SQUAWKS

..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.

ROARING

ROARS

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.

BLOWS

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.

THUNDER RUMBLES

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.

GRUNTS

And that might have led
to starvation.

THUNDER CRACKS

WIND WHOOSHES

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.

GROANS

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.

THUNDER RUMBLES

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.

SQUEAKS

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.

SQUEAKS

CRUNCHING

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...

BARKS

..would've been to run.

But it may have had
another defensive trick.

ROARS

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.

LAUGHS

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.

SQUEAKING

SQUAWKS

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.

RUMBLING

ANIMAL CALLS

All the while,
the creatures at Tanis

go about their business...

CACOPHONY OF
ANIMAL NOISES

..just like any other day.

COOING

CLICKING

WARBLES

SNEEZES

THUNDER RUMBLES

SQUAWKS

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.

GRUNTING

DEEP BELLOWING

The blast from the impact
never reaches Tanis,

but seismic shock waves do.

RUMBLING

CHIRPS

They are far more powerful

than any earthquake
ever recorded.

DEEP BELLOWING

SHRIEKING

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.

THUNDER CRACKS

Next, it begins to rain.

PATTERING

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.

ROARS

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..

ROARS

..or in the air.

SHRIEKS

GRUNTS

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.