Horizon (1964–…): Season 37, Episode 7 - Extreme Dinosaurs - full transcript
Patagonia, Argentina.
This is dinosaur country,
a land where the rocks
are rich with fossils.
For millions of years, this peaceful land
has kept a terrible secret,
and only now are paleontologists
uncovering the truth.
New finds here in South America
are revolutionizing our picture
of the prehistoric world.
It seems that in the time of the dinosaurs
Patagonia may have been the scene
of the bloodiest battle in the history of life -
one that matched the biggest animal
ever to walk the Earth
against a new dinosaur, the most
fearsome killer that has ever evolved.
A huge plant-eating dinosaur
takes on a massive carnivore
in an ugly pitched battle for survival.
This idea of the two biggest creatures
on the planet locked in mortal combat
has proved irresistible to science
fiction writers and movie makers.
But for the scientists who study
dinosaurs, this was pure fantasy.
They knew that this clash of titans
could never have happened in real life.
That's because in real life
the giant long-necked herbivores
never lived alongside the mega-carnivores,
huge dinosaurs like Tyrannosaurus rex,
the king of the meat-eaters.
The two giants never walked the Earth
at the same time in the same place.
Creatures like these could never have met.
Or so the scientists thought.
Plaza Huincul, a small
Argentinian town in rural Patagonia,
is famous for two things: oil and dinosaurs.
Paleontologists come to the plains
around Plaza Huincul
searching for clues to a prehistoric world.
This place was once home
to the most extreme dinosaurs ever seen.
Dinosaur hunter Rodolfo Coria
knows he is a lucky man.
He is chief paleontologist here
and many of the most extraordinary finds
have been his.
Argentina is a good place for finding fossils,
especially because of Patagonia.
Patagonia is almost 50 per cent
of the Argentinian surface,
and the rocks, they are very well exposed.
So it is very easy to find fossil evidence.
If you are looking for dinosaurs,
Patagonia is the place.
(NARRATOR) Even Rodolfo was unprepared
for the record-breaking monsters
he was to unearth in these rocks,
dinosaurs which would change our picture
of the prehistoric world.
It all began nine years ago,
when he began excavating the bones
of what was obviously a very large dinosaur.
After many days of back-breaking digging,
they had revealed just part
of an enormous skeleton.
They hauled whole chunks of rock back
to the workshop to free the bones inside.
The amazing thing was, when they
chipped away at this massive hunk,
they found only one bone inside.
When they calculated
the size of the creature,
they realized they had found
the biggest dinosaur that ever lived,
a completely new species, a giant plant-eater.
They named this new creature
Argentinosaurus.
This is a human backbone.
This is...a backbone of a whale.
And this is an Argentinosaurus backbone.
You can see, just from its size,
that an Argentinosaurus was a very big animal.
(NARRATOR)
The other bones were just as massive.
With thighs the size of a car,
Argentinosaurus was far and away
the heaviest dinosaur ever found.
When this animal walked, the earth trembled.
The world of paleontology was thrilled.
(NEW SPEAKER) It's an immense plant-eater.
It's perhaps 80 to 100 metric tonnes.
It's the size of a herd of elephants.
It may be that there are dinosaurs
even bigger than Argentinosaurus.
But at present, that's as big as we know
any land-living creature has ever been.
(NARRATOR)
This replica of Argentinosaurus
is being built for the town square
in Plaza Huincul.
When it's finished, it will stand
as tall as a five-storey building.
It wasn't just this dinosaur's size
that was out of the ordinary.
When scientists analyzed the layers
of rock in which the skeleton was found,
they discovered something.
Argentinosaurus, along with many
smaller South American long-necks,
had been living at the wrong time.
This fact was to prove crucial.
Layers of fossil-bearing rock
have shown that dinosaurs
roamed the planet for 180 million years.
Over the course of this time,
hundreds of different species
evolved and died out.
By the middle of their time on Earth,
the Jurassic Period,
the land was dominated by massive
plant-eating dinosaurs, the long-necks.
These giant animals lumbered slowly
across the landscape in large herds.
With tiny brains the size of a golf ball,
they were neither quick-witted
nor fleet-footed. They didn't need to be.
Sheer size was their defense.
Only the youngest or the sickest
were at risk from smaller predators.
The reign of the long-necks
lasted for 60 million years,
and then they died out; no one knows why.
By the end of the final age of dinosaurs,
the Cretaceous Period,
things were very different.
A new and more vicious species
of dinosaur arrived on the scene,
the massive carnivorous tyrannosaurs.
They were enormous. They were
the biggest carnivores known.
For the next 25 million years,
these huge meat-eaters
preyed upon everything around them.
These giant predators never met
the long-necked herbivores.
But there was a part of the world
where evolution took a different path...
South America.
Millions of years ago,
when dinosaurs first appeared,
all the land was connected
in one huge super-continent, Pangea.
Over the ages, Pangea broke up
into two giant land masses,
one in the north and one in the south.
(NEW SPEAKER) Probably around 100 million
years ago, South America became separated.
And then the dinosaurs, the mammals,
the rest of the fauna and flora
started to evolve in separate ways,
in different ways.
(NARRATOR) After the continent split,
different dinosaurs evolved
on each continent.
While, throughout the northern continents,
the giant long-necks died out,
down south,
something extraordinary was happening.
Here, the huge long-necks not only survived,
they just kept growing bigger and bigger.
About 90 million years ago,
there were not such animals this big
in any other part of the world,
but in South America.
These four-legged plant-eaters,
like Argentinosaurus,
are a typical South American kind of dinosaur.
In this Cretaceous Period,
they were highly successful
in the southern hemisphere.
It wasn't just the plant-eaters
that were different
on the isolated continent of South America.
Sealed off from the rest of the world,
the tyrannosaurs never reached here.
In the time of the long-neck Argentinosaurus,
scientists could find no trace of any
large meat-eaters stalking the continent.
But all that was about to change.
A few years after the discovery
of Argentinosaurus,
Rodolfo started exploring
a new fossil location near Plaza Huincul.
Little did they realize what
a fearsome creature they would uncover.
Buried for 95 million years,
a new monster
began to emerge from its rocky grave.
When they put the bones together,
they had uncovered
their second record breaker.
This was a truly astonishing find.
But this wasn't a long-necked plant-eater.
It was the skeleton of the biggest
meat-eating dinosaur that ever lived.
It was a new species of animal,
unrelated to the tyrannosaurs.
And it was huge,
the first giant carnivore
ever discovered in South America.
They called it Giganotosaurus.
Giganotosaurus is 10-15 per cent
more massive than Tyrannosaurus rex,
which was the record holder.
Giganotosaurus was an incredible animal,
around 13 meters in length.
The head was huge,
around one meter and 80 centimeters.
(NARRATOR) Giganotosaurus had a skull
the length of a man.
But this giant predator
had one more thing to reveal.
When the team dated the bones, they found
Giganotosaurus lived in the Cretaceous,
the time of the long-neck Argentinosaurus.
The two dinosaurs were found
only 80 kilometers apart.
For the first time anywhere,
scientists had discovered
mega-carnivores and huge plant-eaters
living during the same time period
and in the same place.
This is a peculiar ecological relationship
that we found in Patagonia.
Big preys and big predators.
If we look at South America
in the age of Giganotosaurus,
the main potential prey
for this immense meat-eater
is an even more immense plant-eater,
Argentinosaurus.
(NARRATOR) Could it be that in Patagonia
something unique happened?
That the largest-ever plant-eater
came face-to-face
with the largest meat-eater
in an extraordinary clash of the titans?
(ROARING)
Could this really ever have happened?
As paleontologists considered the idea,
they immediately saw a problem.
The giant meat-eater, Giganotosaurus,
may have been large,
but he was still no match for Argentinosaurus.
There was no way even this big meat-eater
could have killed such a huge animal.
No way, that is, unless Giganotosaurus
did what many other predators do
when faced with a bigger prey.
For these hyenas, hunting together
is the only way to bring down this wildebeest.
Could this have been
what the clash of titans was like?
Not two solitary dinosaurs
battling it out by themselves,
but a pack of marauding Giganotosaurus
hunting one enormous Argentinosaurus?
Unfortunately, there was
a fundamental problem with this idea.
Paleontologists have traditionally believed
that large carnivorous dinosaurs
lived and hunted alone.
There was no evidence to support
the idea of them as pack hunters.
If they weren't pack hunters, they could
never have attacked Argentinosaurus.
Angela Milner, like many paleontologists,
believes the mega-carnivores
were solitary creatures.
(MILNER)
The traditional view of large meat-eaters
was that they were large, ferocious
animals, perhaps rabid predators,
but probably living singly.
There's no real evidence at all
that they worked together in big groups.
Pack hunting is really hard to evolve.
Unless there's a reason for it to be there,
my default would be to say it's not there.
(NARRATOR) For the skeptics, evidence
supports their view of solitary predators.
These are footprints made by dinosaurs.
They've been preserved in rock
for over 150 million years.
Mark Norell believes such footprints
show which dinosaurs lived in groups.
The biggest plant-eating dinosaurs
left track-ways, fossilized footprints,
which really show
that they lived in groups or herds,
whatever you want to call them.
These footprints are not arranged randomly,
they're arranged in groups.
Large ones walked in front of the packs,
and these groups had a structure
and they're all going in the same direction.
You can follow them for long stretches,
hundreds and thousands of meters.
And you can see that they all move,
they all turn, they're moving together.
It's not just a coincidence.
This is really powerful evidence,
suggestive of this sort of behavior.
The evidence for giant
carnivorous dinosaurs isn't as good.
(CARRANO ) We have meat-eating dinosaur
footprints, but they all seem solitary.
Even with a track-way of footprints in a row,
we never seem to have a track-way
that show a group moving together.
Whereas that is common
for the plant-eating dinosaur footprints,
it's absent for the meat-eating dinosaurs.
(NARRATOR) Another key piece of evidence
supports the view that plant-eating
dinosaurs were group animals.
This desolate landscape contains a bone bed,
a collection of dinosaur bones buried together.
The fossilized remains of plant-eating
dinosaurs, all of the same species,
carpet an area the size of a football pitch.
(MILNER) This bone bed is full
of horned dinosaurs of different ages -
little babies, large full-grown ones.
They were probably crossing a swollen river
and got drowned trying to cross.
Sites where many plant-eating dinosaurs
have been killed in an accident
lead paleontologists to believe
these herbivores were living in herds
when they died together.
(MILNER) With plant-eating dinosaurs,
it's very frequent to find groups of animals
preserved together in the rocks.
Because they're all associated,
and they're mixed ages,
that's good evidence
they were living as a herd.
(NARRATOR) Bone beds of herds
of plant-eating dinosaurs are common.
But there was no such evidence that
meat-eating dinosaurs lived in groups.
In the case of the early fossil finds
of meat-eating dinosaurs,
they reinforce this idea of meat-eaters
as solitary hunters.
People had only found individual
specimens of each of the species.
They never found
a bunch of individuals together.
(NARRATOR) The evidence indicated
these predators lived as solitary hunters.
And if they were solitary hunters,
no single carnivore, however big,
would have gone for a prey as huge
as the giant herbivore, Argentinosaurus.
The tantalizing idea of a clash of the titans
down in Patagonia was doomed.
Or so most paleontologists thought.
But one man was going to change all that.
Phil Currie is one of the world's
most accomplished paleontologists.
He can identify any meat-eating dinosaur
from a single tooth.
Currie's passion for predatory dinosaurs
led him to work with Coria
on the plains of Patagonia.
When an opportunity came up in 1995
to go to Argentina
and see Rodolfo and all the fantastic
finds he'd made, I jumped at it.
(NARRATOR) Currie had always believed
the mega-carnivores were solitary
and didn't hunt in packs.
But over time, as he began to think
things through, he made a connection.
Looking at modern animals,
it became clear
that it wasn't such an unusual thing
that big meat-eating dinosaurs
were pack animals.
We'd had good indications that
the plant-eaters were herding animals.
It made sense
that if the carnivores wanted to break
the defenses of a plant-eater's herd,
the only way they could do that
is by strength of numbers.
One of the responses that happens
in a wide range of animals
is that the meat-eaters become pack hunters.
(NARRATOR) Currie now began to think
the idea of large meat-eating dinosaurs
as pack hunters was a possibility.
But to prove his hunch,
he needed hard evidence,
like that which had been found
for the plant-eaters.
What he needed was to find a bone bed
where a group of mega-carnivores,
no matter what species, lay buried together.
(CURRIE) If we can find a bone bed
with a lot of carnivores in one place,
we have an indication that they died together.
If they died together,
there's a high probability
they may have been living together.
The only way to demonstrate
an animal's a group hunter,
or even come close to thinking
about that, is by finding an assemblage
with multiple individuals of different age sizes,
from small individuals all the way to big adults,
buried together at the same time.
So for Currie, the search was on
around the world for just such a site.
And then...he remembered something.
Several years earlier,
he had read a very old magazine article
by one of the most famous
early dinosaur hunters.
(CURRIE) I read an article by Brown.
The article was basically about
his experiences in southern Alberta.
In that article is basically a one-liner,
which suggests that he found somewhere
where there was a lot of tyrannosaurs'
remains in one single bone bed.
(NARRATOR)
Currie realized this might be
the multiple-carnivore bone bed
he had been looking for,
a place which showed that several
tyrannosaurs had lived and died together.
Buried in the pages of
''National Geographic'' for over 80 years,
the reference to the bone bed site
had long been forgotten.
I got really excited. I knew
that this was a really special site.
And I felt that we had to refind this site.
It wasn't a matter any more that there
was a bone bed that we might find.
I had to find that site.
(NARRATOR) Although finding this site
had become crucial, there was a problem.
Barnum Brown had never written down
where the site was.
He died, taking the secret
of its location to the grave.
This is one of Barnum Brown's field books.
There aren't too many of these,
just because Barnum Brown
didn't take any notes.
All it is is just a list of specimens
and field numbers.
There's not much about his activities,
about the geology of particular localities,
except that the rocks were grey,
or it took him three days to get a specimen out.
Unlike a lot of paleontologists
of his time, or even today,
he wasn't much of a note taker.
(NARRATOR)
Currie needed to find the site.
So he scoured Brown's archive, looking for clues.
(CURRIE) We looked at everything
we could get our hands on.
Amongst all that material were four
photographs which were pretty good.
(NARRATOR) The photographs had been
taken by Brown around the dig site in 1910.
Currie hoped that he could use the photos
to pinpoint Brown's excavation.
All that was known was that the site
lay somewhere in the Badlands,
near the Red Deer River in western Canada.
So in 1997, Currie and a team
of paleontologists set off by boat
down a hundred-mile stretch
of the Red Deer River,
following the paddle strokes
of Barnum Brown, looking for the site.
The Badlands of Canada
stretch over hundreds of square miles,
with endless crags, hills and gullies
that all look exactly the same.
In all this vast land,
no one knew where this potential goldmine
of fossils was located.
(CURRIE)
The Badlands are very, very complex.
Unless you have exactly the right angle,
at the same time of day
as he took the photograph,
the chances are pretty good you can't
relocate sites by using photographs.
(NARRATOR) But as he studied
the photographs, Currie noticed something.
In one of them, Brown's assistant
was working at the elusive site.
Behind him was a distinctive ridge of hills.
If Currie could find that ridge,
he could find the site.
If you look at this photograph,
you can see a series of ridges
with trees behind them.
There's not that many places around
with that combination of ridges and trees.
If you can line yourself up
with those ridges and trees,
you're in the right area and you have
a good chance of finding the quarry.
Even so, it's still like looking
for a needle in a haystack.
We spent a couple of days scouring the area,
looking for the right combination
of Badlands as revealed in the photographs.
The first day went by and we had no luck.
The next day turned out to be
the hottest day of the year.
The expedition, which numbered about
16 people, basically ran out of water.
By lunch time, everybody had gone
back to camp except for me.
I'm crazy enough that I kept at it.
I went through all the Badlands here.
These canyons are quite deep,
so going up and down them on the hottest
day of the year was quite an effort.
There was a point when I suddenly realized
a ridge in this region looked like
it might just have the right viewpoint.
I got to the top,
and as I mounted this ridge over here,
I could see that the trees and the ridge
lined up perfectly.
I knew I had the site.
(NARRATOR) Currie and his team pounced
on this unique site and started digging.
And it was worth it.
What they found were the remains
of several tyrannosaurs, all in one place.
One after another, they kept unearthing
the bones of these huge carnivores.
I don't know if Brown did a head count,
but the minimum number of animals
in this quarry is definitely 12.
(NARRATOR) 12 large meat-eating
dinosaurs buried in the same place.
It was an unprecedented find.
Phil Currie had found the site that he
had dreamed of. But there was more.
As they examined the bones,
it was clear that the dinosaurs were of every age,
from babies up to fully mature adults.
It looked like a pack.
(CURRIE) The range of material
is such that we can see
that the smallest individual in the bone bed
was about four meters long.
And the largest individual is about 11 meters long.
So it's a pretty big range in size.
(NARRATOR) They had found a whole pack.
Here at last was proof that the giant
meat-eaters were not solitary creatures,
that the traditional image was wrong.
Instead, the mega-carnivores may
really have lived and hunted in groups.
If that was true, then down in South America,
packs of Giganotosaurus
might have attacked prey
as enormous as
the immense Argentinosaurus.
Currie's site seemed to prove it all.
But other paleontologists were not yet convinced.
(CARRANO ) Bone beds are tantalizing,
because you have a tremendous number
of bones in one single layer.
It's tempting to look at that
as evidence for a herd of animals,
living in one place at one time.
There are times the information
supports that interpretation.
But there are times when it does not.
(NARRATOR) Before anyone
would endorse Currie,
he would have to verify some key details
about the dig site.
(MILNER) A bone bed doesn't automatically
mean that the animals lived together.
Sometimes bone beds accumulate
from large areas,
where floods have brought
all kinds of remains together.
You might be looking at
an accumulation of many animals,
from miles and miles away.
(NARRATOR) This was the first problem.
Flood waters could have washed together
the remains of several unrelated tyrannosaurs.
Buried in the same place millions of years ago,
today they might look like a pack.
But Currie felt he had an answer to this.
Tyrannosaurs were rare dinosaurs.
They would have made up only five
per cent of the animal life in this area.
The chances that 12 unrelated
tyrannosaurs died separately
and were washed together to this spot
were minute.
To find 12 tyrannosaurs by chance,
at this level, in this bone bed...
The chances of that happening
are about one in 64 million.
It isn't likely
that it's going to happen by chance.
(NARRATOR)
There could be an even more dramatic reason
why the bones of Currie's tyrannosaurs
were all in one place.
They could all have been caught
in a predator trap.
This is a predator trap.
In this strange swamp-like place,
molten tar has bubbled up
from deep within the Earth
for tens of thousands of years.
The sticky tar is lethal
to any animal that wanders into it.
Within seconds, the creature will become stuck,
and then its fate is sealed.
Predator traps have been found
all around the world.
This one is in downtown Los Angeles.
John Harris has been investigating
these tar pits for the past 20 years.
A horse or a ground sloth or a camel
would wander along,
and get stuck and...
Just demonstrating here...
Once it's in, it takes a great deal
of strength to pull it out.
If an animal gets stuck on the surface
like this,
when it's trying to pull out one leg,
it's pushing in three others.
Very soon it will get totally immobilized.
(NARRATOR) The trapped animal
would lure predators to the swamp,
who would, in turn, become stuck.
(HARRIS) It would be meat on the hoof,
waiting for the sabre-tooths to feed.
They would come in and, in turn, get stuck.
Down would come vultures and they'd get stuck.
In would come the flies, and they'd get stuck.
In short order,
you'd build up the whole food chain.
(NARRATOR) Over time, hundreds of dinosaurs
would have sunk into traps.
Millions of years later,
the tar and mud has turned to rock,
the bones fossilized, and the site would
look like any normal rocky bone bed.
If Currie's site was actually
a prehistoric predator trap,
it would destroy his theory that
the tyrannosaurs hunted in packs.
But how could the paleontologists tell?
There is always one telltale feature
of all predator traps.
They trap and kill every animal that
is unlucky enough to cross their path.
They contain the bones of many different
species that lived for miles around.
Over the last century, we've recovered
three and a half million fossils,
representing more than 650 species
of animals and plants.
They include a great diversity of large animals,
mammoths, mastadons, sabre-tooth cats,
lions, dire wolves and so on.
(NARRATOR) If Currie's team
discovered many species at their site,
they would have to consider whether they
were the leftovers of a predator trap.
But after three years of painstaking digging,
there's been one extraordinary finding
about this site.
(CURRIE) So far, all of the animals that
we've found in here as parts of skeletons
are one species,
and that's this big meat-eater,
a tyrannosaur known as Albertosaurus.
There are no other carnivorous dinosaurs
in this bone bed.
Given that we're dealing with
only one type of carnivore,
we can rule out things like predator traps.
It's almost certain
these dinosaurs died here together
because they were living together.
(NARRATOR) Phil Currie
seemed to have proved his case.
But he hadn't.
Although he was convinced, his fellow
paleontologists still weren't sure.
If we just found one site with large
predatory dinosaurs,
found as a group with multiple
individuals of different age sizes,
that could be a fluke, a chance.
The evidence is a little bit equivocal.
It's not definite.
It's a little circumstantial.
(NARRATOR) Despite all his efforts,
Currie's case was not yet proven.
He needed a second site
to convince his colleagues
that the first dig wasn't a fluke,
that large meat-eating dinosaurs
really were pack hunters.
And then he got some unexpected news.
Patagonia, which had harbored the bones
of Argentinosaurus and Giganotosaurus,
had yielded one further treasure.
Phil Currie's colleague, Rodolfo Coria,
had made a new discovery.
We came here
because a local farmer called us
because of some fossils that he had found.
We were very lucky,
because looking in the slope of this hill,
we found this bone.
(NARRATOR) This is a toe bone of what
was to prove to be an enormous dinosaur.
Rodolfo had recognized
that the bone was from a meat-eater,
and the following year he persuaded
Phil Currie to join him in Patagonia,
to try and find the rest of the skeleton.
(CURRIE) We found the level
where the bones were coming from.
As we dug in, we realized there was
a good part of a skeleton there.
It far surpassed our expectations.
(NARRATOR) Phil and Rodolfo thought
the bones belonged to Giganotosaurus.
But as they examined their new discoveries,
they noticed that the bones had different
shapes from those of Giganotosaurus.
(CORIA) These differences
in the shape of the bones
are a clue for a paleontologist
to identify a new species.
And the shape is telling us that we are
dealing with a new species of meat-eater.
(NARRATOR) They began to measure
the bones of their new beast.
They were bigger than any meat-eater bones
ever found anywhere in the world.
Bigger than T-rex,
bigger even than Giganotosaurus.
A full-sized Tyrannosaurus rex was
between 12 and 13 meters in total length.
That means that the new one
was somewhere between 14 and 15 meters.
It looks like we've probably got
the biggest meat-eater in the world.
(NARRATOR) But there was more.
When Rodolfo and his team
began to study the bones in detail,
they noticed something strange.
As they analyzed the bones,
Rodolfo realized
that they had found four leg bones...
..for a two-legged creature.
There was more than one carnivore
in this dinosaur graveyard.
So far, our record is indicating
that at least six individuals have been preserved.
(NARRATOR) What's more,
they were all different ages.
With six specimens of the new meat-eating
dinosaur found at the Argentinian site,
Phil Currie had what he needed -
the second pack of mega-carnivores.
I just couldn't believe it.
Suddenly we had two large meat-eating
dinosaurs in two parts of the world
which were showing packing behavior.
It seems to me
that we have convincing evidence
that large meat-eating dinosaurs
formed these social groups,
where the young and the old
hunted together and lived together.
(NARRATOR) Finally, Currie's discoveries
are beginning to convince others.
(HOLTZ) On the basis of these discoveries,
we're beginning to have to change our ideas
on how large predators behaved.
If they're operating as a group, as a pack,
a group of Giganotosaurus
might have been able to mob
even a big Argentinosaurus -
something no one suspected before.
(NARRATOR) But for Phil Currie,
this idea was more than a suspicion.
It made sense to him that the giant
meat-eaters preyed upon the long-necks.
He was convinced by their teeth.
(CURRIE) The teeth are better adapted
for going after really big dinosaurs,
like the long-necked plant-eaters
in that region.
If you look at the teeth,
the teeth are very blade-like.
They have serrations
down the front and the back,
and the teeth themselves
are very narrow and knife-like.
This is a slicing tooth,
designed to cut through meat.
So this new form could bite
and slice out big chunks of flesh.
(NARRATOR)
The long-necks had massive bones,
impossible to crunch through.
So the giant South American carnivores
didn't even try.
Instead, Currie believes they used
their thin steak-knife teeth
to strip flesh
from around the enormous bones.
They were probably moving in to take quick bites,
slicing off only the flesh
and not biting very deep at all.
Then they'd come in again and take another bite,
until the prey was weak enough to kill.
(NARRATOR) So when a group
attacked together in a pack,
even a huge Argentinosaurus was doomed.
It looks like the clash of titans
could really have happened, after all.
(ROARING)
(DEEP GROWLING)
This is dinosaur country,
a land where the rocks
are rich with fossils.
For millions of years, this peaceful land
has kept a terrible secret,
and only now are paleontologists
uncovering the truth.
New finds here in South America
are revolutionizing our picture
of the prehistoric world.
It seems that in the time of the dinosaurs
Patagonia may have been the scene
of the bloodiest battle in the history of life -
one that matched the biggest animal
ever to walk the Earth
against a new dinosaur, the most
fearsome killer that has ever evolved.
A huge plant-eating dinosaur
takes on a massive carnivore
in an ugly pitched battle for survival.
This idea of the two biggest creatures
on the planet locked in mortal combat
has proved irresistible to science
fiction writers and movie makers.
But for the scientists who study
dinosaurs, this was pure fantasy.
They knew that this clash of titans
could never have happened in real life.
That's because in real life
the giant long-necked herbivores
never lived alongside the mega-carnivores,
huge dinosaurs like Tyrannosaurus rex,
the king of the meat-eaters.
The two giants never walked the Earth
at the same time in the same place.
Creatures like these could never have met.
Or so the scientists thought.
Plaza Huincul, a small
Argentinian town in rural Patagonia,
is famous for two things: oil and dinosaurs.
Paleontologists come to the plains
around Plaza Huincul
searching for clues to a prehistoric world.
This place was once home
to the most extreme dinosaurs ever seen.
Dinosaur hunter Rodolfo Coria
knows he is a lucky man.
He is chief paleontologist here
and many of the most extraordinary finds
have been his.
Argentina is a good place for finding fossils,
especially because of Patagonia.
Patagonia is almost 50 per cent
of the Argentinian surface,
and the rocks, they are very well exposed.
So it is very easy to find fossil evidence.
If you are looking for dinosaurs,
Patagonia is the place.
(NARRATOR) Even Rodolfo was unprepared
for the record-breaking monsters
he was to unearth in these rocks,
dinosaurs which would change our picture
of the prehistoric world.
It all began nine years ago,
when he began excavating the bones
of what was obviously a very large dinosaur.
After many days of back-breaking digging,
they had revealed just part
of an enormous skeleton.
They hauled whole chunks of rock back
to the workshop to free the bones inside.
The amazing thing was, when they
chipped away at this massive hunk,
they found only one bone inside.
When they calculated
the size of the creature,
they realized they had found
the biggest dinosaur that ever lived,
a completely new species, a giant plant-eater.
They named this new creature
Argentinosaurus.
This is a human backbone.
This is...a backbone of a whale.
And this is an Argentinosaurus backbone.
You can see, just from its size,
that an Argentinosaurus was a very big animal.
(NARRATOR)
The other bones were just as massive.
With thighs the size of a car,
Argentinosaurus was far and away
the heaviest dinosaur ever found.
When this animal walked, the earth trembled.
The world of paleontology was thrilled.
(NEW SPEAKER) It's an immense plant-eater.
It's perhaps 80 to 100 metric tonnes.
It's the size of a herd of elephants.
It may be that there are dinosaurs
even bigger than Argentinosaurus.
But at present, that's as big as we know
any land-living creature has ever been.
(NARRATOR)
This replica of Argentinosaurus
is being built for the town square
in Plaza Huincul.
When it's finished, it will stand
as tall as a five-storey building.
It wasn't just this dinosaur's size
that was out of the ordinary.
When scientists analyzed the layers
of rock in which the skeleton was found,
they discovered something.
Argentinosaurus, along with many
smaller South American long-necks,
had been living at the wrong time.
This fact was to prove crucial.
Layers of fossil-bearing rock
have shown that dinosaurs
roamed the planet for 180 million years.
Over the course of this time,
hundreds of different species
evolved and died out.
By the middle of their time on Earth,
the Jurassic Period,
the land was dominated by massive
plant-eating dinosaurs, the long-necks.
These giant animals lumbered slowly
across the landscape in large herds.
With tiny brains the size of a golf ball,
they were neither quick-witted
nor fleet-footed. They didn't need to be.
Sheer size was their defense.
Only the youngest or the sickest
were at risk from smaller predators.
The reign of the long-necks
lasted for 60 million years,
and then they died out; no one knows why.
By the end of the final age of dinosaurs,
the Cretaceous Period,
things were very different.
A new and more vicious species
of dinosaur arrived on the scene,
the massive carnivorous tyrannosaurs.
They were enormous. They were
the biggest carnivores known.
For the next 25 million years,
these huge meat-eaters
preyed upon everything around them.
These giant predators never met
the long-necked herbivores.
But there was a part of the world
where evolution took a different path...
South America.
Millions of years ago,
when dinosaurs first appeared,
all the land was connected
in one huge super-continent, Pangea.
Over the ages, Pangea broke up
into two giant land masses,
one in the north and one in the south.
(NEW SPEAKER) Probably around 100 million
years ago, South America became separated.
And then the dinosaurs, the mammals,
the rest of the fauna and flora
started to evolve in separate ways,
in different ways.
(NARRATOR) After the continent split,
different dinosaurs evolved
on each continent.
While, throughout the northern continents,
the giant long-necks died out,
down south,
something extraordinary was happening.
Here, the huge long-necks not only survived,
they just kept growing bigger and bigger.
About 90 million years ago,
there were not such animals this big
in any other part of the world,
but in South America.
These four-legged plant-eaters,
like Argentinosaurus,
are a typical South American kind of dinosaur.
In this Cretaceous Period,
they were highly successful
in the southern hemisphere.
It wasn't just the plant-eaters
that were different
on the isolated continent of South America.
Sealed off from the rest of the world,
the tyrannosaurs never reached here.
In the time of the long-neck Argentinosaurus,
scientists could find no trace of any
large meat-eaters stalking the continent.
But all that was about to change.
A few years after the discovery
of Argentinosaurus,
Rodolfo started exploring
a new fossil location near Plaza Huincul.
Little did they realize what
a fearsome creature they would uncover.
Buried for 95 million years,
a new monster
began to emerge from its rocky grave.
When they put the bones together,
they had uncovered
their second record breaker.
This was a truly astonishing find.
But this wasn't a long-necked plant-eater.
It was the skeleton of the biggest
meat-eating dinosaur that ever lived.
It was a new species of animal,
unrelated to the tyrannosaurs.
And it was huge,
the first giant carnivore
ever discovered in South America.
They called it Giganotosaurus.
Giganotosaurus is 10-15 per cent
more massive than Tyrannosaurus rex,
which was the record holder.
Giganotosaurus was an incredible animal,
around 13 meters in length.
The head was huge,
around one meter and 80 centimeters.
(NARRATOR) Giganotosaurus had a skull
the length of a man.
But this giant predator
had one more thing to reveal.
When the team dated the bones, they found
Giganotosaurus lived in the Cretaceous,
the time of the long-neck Argentinosaurus.
The two dinosaurs were found
only 80 kilometers apart.
For the first time anywhere,
scientists had discovered
mega-carnivores and huge plant-eaters
living during the same time period
and in the same place.
This is a peculiar ecological relationship
that we found in Patagonia.
Big preys and big predators.
If we look at South America
in the age of Giganotosaurus,
the main potential prey
for this immense meat-eater
is an even more immense plant-eater,
Argentinosaurus.
(NARRATOR) Could it be that in Patagonia
something unique happened?
That the largest-ever plant-eater
came face-to-face
with the largest meat-eater
in an extraordinary clash of the titans?
(ROARING)
Could this really ever have happened?
As paleontologists considered the idea,
they immediately saw a problem.
The giant meat-eater, Giganotosaurus,
may have been large,
but he was still no match for Argentinosaurus.
There was no way even this big meat-eater
could have killed such a huge animal.
No way, that is, unless Giganotosaurus
did what many other predators do
when faced with a bigger prey.
For these hyenas, hunting together
is the only way to bring down this wildebeest.
Could this have been
what the clash of titans was like?
Not two solitary dinosaurs
battling it out by themselves,
but a pack of marauding Giganotosaurus
hunting one enormous Argentinosaurus?
Unfortunately, there was
a fundamental problem with this idea.
Paleontologists have traditionally believed
that large carnivorous dinosaurs
lived and hunted alone.
There was no evidence to support
the idea of them as pack hunters.
If they weren't pack hunters, they could
never have attacked Argentinosaurus.
Angela Milner, like many paleontologists,
believes the mega-carnivores
were solitary creatures.
(MILNER)
The traditional view of large meat-eaters
was that they were large, ferocious
animals, perhaps rabid predators,
but probably living singly.
There's no real evidence at all
that they worked together in big groups.
Pack hunting is really hard to evolve.
Unless there's a reason for it to be there,
my default would be to say it's not there.
(NARRATOR) For the skeptics, evidence
supports their view of solitary predators.
These are footprints made by dinosaurs.
They've been preserved in rock
for over 150 million years.
Mark Norell believes such footprints
show which dinosaurs lived in groups.
The biggest plant-eating dinosaurs
left track-ways, fossilized footprints,
which really show
that they lived in groups or herds,
whatever you want to call them.
These footprints are not arranged randomly,
they're arranged in groups.
Large ones walked in front of the packs,
and these groups had a structure
and they're all going in the same direction.
You can follow them for long stretches,
hundreds and thousands of meters.
And you can see that they all move,
they all turn, they're moving together.
It's not just a coincidence.
This is really powerful evidence,
suggestive of this sort of behavior.
The evidence for giant
carnivorous dinosaurs isn't as good.
(CARRANO ) We have meat-eating dinosaur
footprints, but they all seem solitary.
Even with a track-way of footprints in a row,
we never seem to have a track-way
that show a group moving together.
Whereas that is common
for the plant-eating dinosaur footprints,
it's absent for the meat-eating dinosaurs.
(NARRATOR) Another key piece of evidence
supports the view that plant-eating
dinosaurs were group animals.
This desolate landscape contains a bone bed,
a collection of dinosaur bones buried together.
The fossilized remains of plant-eating
dinosaurs, all of the same species,
carpet an area the size of a football pitch.
(MILNER) This bone bed is full
of horned dinosaurs of different ages -
little babies, large full-grown ones.
They were probably crossing a swollen river
and got drowned trying to cross.
Sites where many plant-eating dinosaurs
have been killed in an accident
lead paleontologists to believe
these herbivores were living in herds
when they died together.
(MILNER) With plant-eating dinosaurs,
it's very frequent to find groups of animals
preserved together in the rocks.
Because they're all associated,
and they're mixed ages,
that's good evidence
they were living as a herd.
(NARRATOR) Bone beds of herds
of plant-eating dinosaurs are common.
But there was no such evidence that
meat-eating dinosaurs lived in groups.
In the case of the early fossil finds
of meat-eating dinosaurs,
they reinforce this idea of meat-eaters
as solitary hunters.
People had only found individual
specimens of each of the species.
They never found
a bunch of individuals together.
(NARRATOR) The evidence indicated
these predators lived as solitary hunters.
And if they were solitary hunters,
no single carnivore, however big,
would have gone for a prey as huge
as the giant herbivore, Argentinosaurus.
The tantalizing idea of a clash of the titans
down in Patagonia was doomed.
Or so most paleontologists thought.
But one man was going to change all that.
Phil Currie is one of the world's
most accomplished paleontologists.
He can identify any meat-eating dinosaur
from a single tooth.
Currie's passion for predatory dinosaurs
led him to work with Coria
on the plains of Patagonia.
When an opportunity came up in 1995
to go to Argentina
and see Rodolfo and all the fantastic
finds he'd made, I jumped at it.
(NARRATOR) Currie had always believed
the mega-carnivores were solitary
and didn't hunt in packs.
But over time, as he began to think
things through, he made a connection.
Looking at modern animals,
it became clear
that it wasn't such an unusual thing
that big meat-eating dinosaurs
were pack animals.
We'd had good indications that
the plant-eaters were herding animals.
It made sense
that if the carnivores wanted to break
the defenses of a plant-eater's herd,
the only way they could do that
is by strength of numbers.
One of the responses that happens
in a wide range of animals
is that the meat-eaters become pack hunters.
(NARRATOR) Currie now began to think
the idea of large meat-eating dinosaurs
as pack hunters was a possibility.
But to prove his hunch,
he needed hard evidence,
like that which had been found
for the plant-eaters.
What he needed was to find a bone bed
where a group of mega-carnivores,
no matter what species, lay buried together.
(CURRIE) If we can find a bone bed
with a lot of carnivores in one place,
we have an indication that they died together.
If they died together,
there's a high probability
they may have been living together.
The only way to demonstrate
an animal's a group hunter,
or even come close to thinking
about that, is by finding an assemblage
with multiple individuals of different age sizes,
from small individuals all the way to big adults,
buried together at the same time.
So for Currie, the search was on
around the world for just such a site.
And then...he remembered something.
Several years earlier,
he had read a very old magazine article
by one of the most famous
early dinosaur hunters.
(CURRIE) I read an article by Brown.
The article was basically about
his experiences in southern Alberta.
In that article is basically a one-liner,
which suggests that he found somewhere
where there was a lot of tyrannosaurs'
remains in one single bone bed.
(NARRATOR)
Currie realized this might be
the multiple-carnivore bone bed
he had been looking for,
a place which showed that several
tyrannosaurs had lived and died together.
Buried in the pages of
''National Geographic'' for over 80 years,
the reference to the bone bed site
had long been forgotten.
I got really excited. I knew
that this was a really special site.
And I felt that we had to refind this site.
It wasn't a matter any more that there
was a bone bed that we might find.
I had to find that site.
(NARRATOR) Although finding this site
had become crucial, there was a problem.
Barnum Brown had never written down
where the site was.
He died, taking the secret
of its location to the grave.
This is one of Barnum Brown's field books.
There aren't too many of these,
just because Barnum Brown
didn't take any notes.
All it is is just a list of specimens
and field numbers.
There's not much about his activities,
about the geology of particular localities,
except that the rocks were grey,
or it took him three days to get a specimen out.
Unlike a lot of paleontologists
of his time, or even today,
he wasn't much of a note taker.
(NARRATOR)
Currie needed to find the site.
So he scoured Brown's archive, looking for clues.
(CURRIE) We looked at everything
we could get our hands on.
Amongst all that material were four
photographs which were pretty good.
(NARRATOR) The photographs had been
taken by Brown around the dig site in 1910.
Currie hoped that he could use the photos
to pinpoint Brown's excavation.
All that was known was that the site
lay somewhere in the Badlands,
near the Red Deer River in western Canada.
So in 1997, Currie and a team
of paleontologists set off by boat
down a hundred-mile stretch
of the Red Deer River,
following the paddle strokes
of Barnum Brown, looking for the site.
The Badlands of Canada
stretch over hundreds of square miles,
with endless crags, hills and gullies
that all look exactly the same.
In all this vast land,
no one knew where this potential goldmine
of fossils was located.
(CURRIE)
The Badlands are very, very complex.
Unless you have exactly the right angle,
at the same time of day
as he took the photograph,
the chances are pretty good you can't
relocate sites by using photographs.
(NARRATOR) But as he studied
the photographs, Currie noticed something.
In one of them, Brown's assistant
was working at the elusive site.
Behind him was a distinctive ridge of hills.
If Currie could find that ridge,
he could find the site.
If you look at this photograph,
you can see a series of ridges
with trees behind them.
There's not that many places around
with that combination of ridges and trees.
If you can line yourself up
with those ridges and trees,
you're in the right area and you have
a good chance of finding the quarry.
Even so, it's still like looking
for a needle in a haystack.
We spent a couple of days scouring the area,
looking for the right combination
of Badlands as revealed in the photographs.
The first day went by and we had no luck.
The next day turned out to be
the hottest day of the year.
The expedition, which numbered about
16 people, basically ran out of water.
By lunch time, everybody had gone
back to camp except for me.
I'm crazy enough that I kept at it.
I went through all the Badlands here.
These canyons are quite deep,
so going up and down them on the hottest
day of the year was quite an effort.
There was a point when I suddenly realized
a ridge in this region looked like
it might just have the right viewpoint.
I got to the top,
and as I mounted this ridge over here,
I could see that the trees and the ridge
lined up perfectly.
I knew I had the site.
(NARRATOR) Currie and his team pounced
on this unique site and started digging.
And it was worth it.
What they found were the remains
of several tyrannosaurs, all in one place.
One after another, they kept unearthing
the bones of these huge carnivores.
I don't know if Brown did a head count,
but the minimum number of animals
in this quarry is definitely 12.
(NARRATOR) 12 large meat-eating
dinosaurs buried in the same place.
It was an unprecedented find.
Phil Currie had found the site that he
had dreamed of. But there was more.
As they examined the bones,
it was clear that the dinosaurs were of every age,
from babies up to fully mature adults.
It looked like a pack.
(CURRIE) The range of material
is such that we can see
that the smallest individual in the bone bed
was about four meters long.
And the largest individual is about 11 meters long.
So it's a pretty big range in size.
(NARRATOR) They had found a whole pack.
Here at last was proof that the giant
meat-eaters were not solitary creatures,
that the traditional image was wrong.
Instead, the mega-carnivores may
really have lived and hunted in groups.
If that was true, then down in South America,
packs of Giganotosaurus
might have attacked prey
as enormous as
the immense Argentinosaurus.
Currie's site seemed to prove it all.
But other paleontologists were not yet convinced.
(CARRANO ) Bone beds are tantalizing,
because you have a tremendous number
of bones in one single layer.
It's tempting to look at that
as evidence for a herd of animals,
living in one place at one time.
There are times the information
supports that interpretation.
But there are times when it does not.
(NARRATOR) Before anyone
would endorse Currie,
he would have to verify some key details
about the dig site.
(MILNER) A bone bed doesn't automatically
mean that the animals lived together.
Sometimes bone beds accumulate
from large areas,
where floods have brought
all kinds of remains together.
You might be looking at
an accumulation of many animals,
from miles and miles away.
(NARRATOR) This was the first problem.
Flood waters could have washed together
the remains of several unrelated tyrannosaurs.
Buried in the same place millions of years ago,
today they might look like a pack.
But Currie felt he had an answer to this.
Tyrannosaurs were rare dinosaurs.
They would have made up only five
per cent of the animal life in this area.
The chances that 12 unrelated
tyrannosaurs died separately
and were washed together to this spot
were minute.
To find 12 tyrannosaurs by chance,
at this level, in this bone bed...
The chances of that happening
are about one in 64 million.
It isn't likely
that it's going to happen by chance.
(NARRATOR)
There could be an even more dramatic reason
why the bones of Currie's tyrannosaurs
were all in one place.
They could all have been caught
in a predator trap.
This is a predator trap.
In this strange swamp-like place,
molten tar has bubbled up
from deep within the Earth
for tens of thousands of years.
The sticky tar is lethal
to any animal that wanders into it.
Within seconds, the creature will become stuck,
and then its fate is sealed.
Predator traps have been found
all around the world.
This one is in downtown Los Angeles.
John Harris has been investigating
these tar pits for the past 20 years.
A horse or a ground sloth or a camel
would wander along,
and get stuck and...
Just demonstrating here...
Once it's in, it takes a great deal
of strength to pull it out.
If an animal gets stuck on the surface
like this,
when it's trying to pull out one leg,
it's pushing in three others.
Very soon it will get totally immobilized.
(NARRATOR) The trapped animal
would lure predators to the swamp,
who would, in turn, become stuck.
(HARRIS) It would be meat on the hoof,
waiting for the sabre-tooths to feed.
They would come in and, in turn, get stuck.
Down would come vultures and they'd get stuck.
In would come the flies, and they'd get stuck.
In short order,
you'd build up the whole food chain.
(NARRATOR) Over time, hundreds of dinosaurs
would have sunk into traps.
Millions of years later,
the tar and mud has turned to rock,
the bones fossilized, and the site would
look like any normal rocky bone bed.
If Currie's site was actually
a prehistoric predator trap,
it would destroy his theory that
the tyrannosaurs hunted in packs.
But how could the paleontologists tell?
There is always one telltale feature
of all predator traps.
They trap and kill every animal that
is unlucky enough to cross their path.
They contain the bones of many different
species that lived for miles around.
Over the last century, we've recovered
three and a half million fossils,
representing more than 650 species
of animals and plants.
They include a great diversity of large animals,
mammoths, mastadons, sabre-tooth cats,
lions, dire wolves and so on.
(NARRATOR) If Currie's team
discovered many species at their site,
they would have to consider whether they
were the leftovers of a predator trap.
But after three years of painstaking digging,
there's been one extraordinary finding
about this site.
(CURRIE) So far, all of the animals that
we've found in here as parts of skeletons
are one species,
and that's this big meat-eater,
a tyrannosaur known as Albertosaurus.
There are no other carnivorous dinosaurs
in this bone bed.
Given that we're dealing with
only one type of carnivore,
we can rule out things like predator traps.
It's almost certain
these dinosaurs died here together
because they were living together.
(NARRATOR) Phil Currie
seemed to have proved his case.
But he hadn't.
Although he was convinced, his fellow
paleontologists still weren't sure.
If we just found one site with large
predatory dinosaurs,
found as a group with multiple
individuals of different age sizes,
that could be a fluke, a chance.
The evidence is a little bit equivocal.
It's not definite.
It's a little circumstantial.
(NARRATOR) Despite all his efforts,
Currie's case was not yet proven.
He needed a second site
to convince his colleagues
that the first dig wasn't a fluke,
that large meat-eating dinosaurs
really were pack hunters.
And then he got some unexpected news.
Patagonia, which had harbored the bones
of Argentinosaurus and Giganotosaurus,
had yielded one further treasure.
Phil Currie's colleague, Rodolfo Coria,
had made a new discovery.
We came here
because a local farmer called us
because of some fossils that he had found.
We were very lucky,
because looking in the slope of this hill,
we found this bone.
(NARRATOR) This is a toe bone of what
was to prove to be an enormous dinosaur.
Rodolfo had recognized
that the bone was from a meat-eater,
and the following year he persuaded
Phil Currie to join him in Patagonia,
to try and find the rest of the skeleton.
(CURRIE) We found the level
where the bones were coming from.
As we dug in, we realized there was
a good part of a skeleton there.
It far surpassed our expectations.
(NARRATOR) Phil and Rodolfo thought
the bones belonged to Giganotosaurus.
But as they examined their new discoveries,
they noticed that the bones had different
shapes from those of Giganotosaurus.
(CORIA) These differences
in the shape of the bones
are a clue for a paleontologist
to identify a new species.
And the shape is telling us that we are
dealing with a new species of meat-eater.
(NARRATOR) They began to measure
the bones of their new beast.
They were bigger than any meat-eater bones
ever found anywhere in the world.
Bigger than T-rex,
bigger even than Giganotosaurus.
A full-sized Tyrannosaurus rex was
between 12 and 13 meters in total length.
That means that the new one
was somewhere between 14 and 15 meters.
It looks like we've probably got
the biggest meat-eater in the world.
(NARRATOR) But there was more.
When Rodolfo and his team
began to study the bones in detail,
they noticed something strange.
As they analyzed the bones,
Rodolfo realized
that they had found four leg bones...
..for a two-legged creature.
There was more than one carnivore
in this dinosaur graveyard.
So far, our record is indicating
that at least six individuals have been preserved.
(NARRATOR) What's more,
they were all different ages.
With six specimens of the new meat-eating
dinosaur found at the Argentinian site,
Phil Currie had what he needed -
the second pack of mega-carnivores.
I just couldn't believe it.
Suddenly we had two large meat-eating
dinosaurs in two parts of the world
which were showing packing behavior.
It seems to me
that we have convincing evidence
that large meat-eating dinosaurs
formed these social groups,
where the young and the old
hunted together and lived together.
(NARRATOR) Finally, Currie's discoveries
are beginning to convince others.
(HOLTZ) On the basis of these discoveries,
we're beginning to have to change our ideas
on how large predators behaved.
If they're operating as a group, as a pack,
a group of Giganotosaurus
might have been able to mob
even a big Argentinosaurus -
something no one suspected before.
(NARRATOR) But for Phil Currie,
this idea was more than a suspicion.
It made sense to him that the giant
meat-eaters preyed upon the long-necks.
He was convinced by their teeth.
(CURRIE) The teeth are better adapted
for going after really big dinosaurs,
like the long-necked plant-eaters
in that region.
If you look at the teeth,
the teeth are very blade-like.
They have serrations
down the front and the back,
and the teeth themselves
are very narrow and knife-like.
This is a slicing tooth,
designed to cut through meat.
So this new form could bite
and slice out big chunks of flesh.
(NARRATOR)
The long-necks had massive bones,
impossible to crunch through.
So the giant South American carnivores
didn't even try.
Instead, Currie believes they used
their thin steak-knife teeth
to strip flesh
from around the enormous bones.
They were probably moving in to take quick bites,
slicing off only the flesh
and not biting very deep at all.
Then they'd come in again and take another bite,
until the prey was weak enough to kill.
(NARRATOR) So when a group
attacked together in a pack,
even a huge Argentinosaurus was doomed.
It looks like the clash of titans
could really have happened, after all.
(ROARING)
(DEEP GROWLING)