Horizon (1964) s37e07 Episode Script

Extreme Dinosaurs

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 isa 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 thenhe 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.