(GROWLING)
JOHN HURT: We are living through a dinosaur revolution.
We have pushed the boundaries of our knowledge further than ever before.
(ROARS)
We have a completely new understanding
of the greatest killers ever to walk the Earth.
(GROWLING)
One killer, first discovered in Egypt,
has become the icon of these new predators.
A giant dinosaur, with two-metre-long spines rising over its back.
It was unlike anything seen before.
It was only in 2005, when a complete upper jaw was found,
that we could accurately reconstruct this bizarre creature.
With a skull almost two metres long,
this dinosaur was a colossal 17 metres from nose to tail.
Four metres longer than T-Rex.
The reign of the dinosaurs began almost 250 million years ago,
but this killer didn't appear until a time known as the mid-Cretaceous.
95 million years ago, its home in North Africa
was a desert surrounding a vast system of rivers and swamps.
The swamps are refuges for many large dinosaurs,
like the duck-billed Ouranosaurus.
(SQUAWKS)
(CALLING)
They are also the hunting grounds for a killer.
(CALLING)
(GROWLING)
Spinosaurus,
the biggest killer ever to walk the earth.
An 11-tonne colossus.
However, for the time being,
these Ouranosaurs are off this killer's menu.
Spinosaurus is part of a relatively newly discovered family of dinosaurs.
They've been found in South America with Irritator,
in Europe, there's Baryonyx,
and Asia, Siamosaurus.
But the last and biggest of all came from North Africa:
Spinosaurus itself.
And studies of their bones and teeth revealed something amazing.
Spinosaurus is a predator,
but one that hunts in water.
Spinosaurus is unique.
With long, narrow jaws and nostrils set high on its head,
its teeth were straight and conical,
and it had a curious pattern of holes in its snout,
which give us a clue to how it hunted.
These are Onchopristis,
eight-metre-long giant sawfish.
In 2008, a Spinosaurus skull was put through a CT scanner.
It revealed that the holes and sinuses in the snout
looked just like those of crocodiles.
It's thought these contained pressure sensors.
Sensors that, like a crocodile,
can detect the movement of prey.
It can strike without even seeing its victim.
Anywhere else, this eight-metre Rugops might be the top carnivore.
But here, it is dwarfed by Spinosaurus,
a predator that adapted to exploit an environment so successfully
it evolved into a 17-metre giant.
Spinosaurus is the biggest dinosaur predator ever discovered,
but it wasn't the first giant killer.
The first giant killer dinosaurs appeared much earlier.
They lived in the Jurassic period, 150 million years ago.
One of the most iconic is Allosaurus,
from the Morrison Formation in North America.
Yet it's only recently that we have been able to work out
how these predators hunted.
(WIND HOWLING)
(SNUFFLING)
Allosaurus is the most common killer in these lands.
Nine metres long, with a battery of saw blade-like teeth,
Allosaurus is a formidable hunter.
A lone Camptosaurus should be an easy kill.
Allosaurus teeth were serrated front and back,
perfectly evolved for tearing through flesh.
However, recent research has indicated
that Allosaurus's bite was surprisingly weak.
Calculations suggested its bite was less powerful than a lion's.
So just how did this jurassic monster hunt and kill?
(SQUEAKS NERVOUSLY)
Camptosaurus relies on its keen senses to avoid predators.
Allosaurus, on the other hand, is a fast and powerful ambush hunter.
(ROARING)
(GROANING)
(MOANING WEAKLY)
(ROARING)
Despite the apparent weakness of its bite,
Allosaurus did, in fact, have a deadly killing method.
Its skull could withstand a force more than 15 times as great as its bite.
This meant that Allosaurus used its head like an axe,
its strong neck muscles driving its top jaw into its prey.
With every impact, the serrated teeth would tear through its prey's flesh...
the victim dying through a combination of shock and blood loss.
(ROARING)
Saurophaganax.
At 12 metres, it is the biggest carnivore in the region.
(ROARING)
(BOTH ROARING)
One of the advantages of being so big
is that stealing another's kill is that much easier.
With the rise of giant predators,
and their spread throughout the Jurassic world,
smaller dinosaurs needed new strategies if they were to survive.
In recent years, China has been the focus
of some remarkable fossil discoveries.
One extraordinary fossil hints
how some may have avoided these killer dinosaurs.
It lived in the Jurassic forests of China 154 million years ago.
Hiding in these lush forests is Epidexipteryx.
This forest is home to many predators, and being small makes it vulnerable.
(DISTANT ROARING)
This is Sinraptor.
A small dinosaur like Epidexipteryx
would be of no interest to a seven-metre adult.
But this is a juvenile.
(ROARING)
Being small does have its advantages.
Everything we know about Epidexipteryx
comes from an incredible fossil first revealed in 2008.
It showed an animal with a small skull and large eye sockets
and unusually long teeth,
with toes suited to gripping branches and very long arms and hands.
It suggests that this was a dinosaur well suited to living in the trees.
The extraordinary elongated third finger
is another distinctive feature of the group.
With this and its projecting front teeth,
Epidexipteryx has the perfect tools to hunt for insects.
(INSECT BUZZING)
Prey like this, which is difficult to catch, is quite a prize.
A prize that can attract unwanted attention.
Here it's another, larger, Epidexipteryx.
(SQUAWKING)
(BOTH SQUAWKING)
There is more to this extraordinary creature than first meets the eye.
The fossil has also revealed
that it was covered in short, simple feathers.
Feathers that were likely to have evolved for just one reason:
to keep it warm.
But there is one last striking feature:
four long feathers on its tail.
These feathers aren't like those of modern birds.
These are long and ribbon-like,
almost certainly only for show.
They're the earliest record of ornamental feathers.
In fact, the very name "Epidexipteryx" means "display feather".
(SQUAWKING)
And they're among the most bird-like of any dinosaur.
Only in the trees can you be safe from large predators like Sinraptor.
Moving into the trees opened up an entirely new world for dinosaurs.
And it wasn't long before killers followed.
The most dramatic, found in 2000,
lived in northeast China around 120 million years ago,
at the beginning of the Cretaceous period.
A dinosaur that took tree-living to a whole new level.
This is Xianglong.
With prey like this, predators were sure to follow.
Microrapter.
Microraptor is small, and well adapted to chasing prey in the canopy.
Xianglong, however, has a trick.
This is a flying lizard.
And the exquisite fossils of Microraptor revealed a surprise.
The feathers of this dinosaur aren't for keeping warm, or for show.
Their structure is plainly visible from the fossils.
They are very long, veined and, most importantly,
their shape creates a perfect aerodynamic surface.
And they aren't confined to its forearms.
Its legs, too, had long feathers.
These feathers are designed for one thing only:
flight.
Microraptor is a four-winged dinosaur that took to the skies.
But Microraptor isn't the only flying monster here.
Sinornithosaurus, more than capable of stealing prey.
But it has a bigger prize in mind.
(GROANS)
And Sinornithosaurus has a deadly secret.
In 2009, a study of Sinornithosaurus
found distinctive grooves along the length of its teeth.
They resemble those of the venomous Gila monster,
the grooves of its teeth used to deliver venom into its victim.
The team even identified what they thought
was the location of the venom sack in the fossil.
It appeared Sinornithosaurus could kill with poison.
Having longer flight feathers on both its arms and legs,
Microraptor is by far the better glider.
But with no ability to gain height,
the only way is down.
Microraptor's long feathers mean it can barely walk, much less run.
Sinornithosaurus has no such problem.
On the forest floor, the tables are turned.
Microraptor has a fortunate escape.
Killer dinosaurs dominated the land, the trees,
and had even taken to the air.
But by the middle of the Cretaceous period, things were changing.
A new breed of killers was emerging.
These were the famed Tyrannosaurs.
Formidable hunter-killers that swept aside almost all other predators.
Carnivorous dinosaurs that remained were forced to adapt,
sometimes going to extreme lengths.
One such group was the bizarre Therizinosaurs.
In 2009, the most complete skeleton found so far was described.
It lived in New Mexico 92 million years ago.
(GROWLING)
These swamps are home to Zunityrannus,
a mid-sized Tyrannosaur.
And they're also home to this weird creature,
Nothronychus.
It's actually a close relative of the Tyrannosaur,
but with one major difference.
Nothronychus has given up eating meat.
(GROWLING)
(ROARING)
Therizinosaurs had been a mystery for decades,
known only from tantalising fragments.
That all changed with the discovery of Nothronychus.
It gave us our clearest look at this strange group of dinosaurs.
It walked upright on short, stocky legs,
it had wide hips and a long neck.
Its teeth showed that these weren't the teeth of a killer.
Far from its ferocious Tyrannosaur cousins,
this pot-bellied dinosaur had evolved into a strict vegetarian.
But armed with viciously long claws on its forearms,
it was by no means defenceless.
(GROWLING)
By becoming a plant eater, Nothronychus has easy access to food.
(GROWLS)
Nothronychus thrives here
because it doesn't compete with the Tyrannosaurs.
But just because you're not competing for food
doesn't mean you're not seen as food.
(GROWLING)
Over the next few million years,
Tyrannosaurs evolved, getting bigger and more deadly.
They developed into the ultimate predators
and dominated virtually all of Asia and North America.
The most famous of these might be T-Rex,
but it was just the last in a long line of giant killers.
75 million years ago, North America was home
to the original giant Tyrannosaur,
Daspletosaurus.
Its effectiveness as a killer is clear from its anatomy.
It's massive, with a huge, strong skull and a powerful, muscular neck.
Forward-facing eyes make tracking moving prey easy.
They've famously short arms,
but with these giant Tyrannosaurs, it's all about the bite.
Daspletosaurus,
with a bite force unmatched by any other dinosaur in the region.
This is a killer in a completely different league.
(GROWLING)
(ROARING)
This group have congregated to take advantage of an annual event.
A vast herd of Centrosaurus is on the move.
Unwittingly, they're walking towards almost certain death.
In Dinosaur Provincial Park,
thousands of bones have been discovered
scattered across the same rock layer.
They belong to the horned dinosaur Centrosaurus.
And they appear to be the bone beds of vast killing fields,
sites of wholesale slaughter.
Seasonal monsoons drives the Centrosaurs inland,
away from coastal flooding.
(THUNDER CLAPPING)
(ROARING)
Herding behaviour protects the many,
but at the expense of the few.
And things are about to get worse for the Centrosaurs.
With a flooded river ahead
and the Daspletosaurus behind,
the stage is now set for a massacre.
But despite the rich pickings, it's not the Daspletosaurus
that are responsible for the scale of the slaughter.
There's an even more deadly killer at work here.
The real killer is the weather itself.
Recent studies of this dense bone bed indicate
that 96% of the bones are of a single species, Centrosaurus.
And relatively few of the bones display any bite marks.
The fossil evidence suggests that this was a mass drowning,
the result of widespread seasonal flooding.
An event that we have seen repeated in over 20 different sites.
And when the waters recede, new opportunities emerge.
(SCREECHING)
But even in the fight for rotting flesh,
Daspletosaurus's authority is absolute.
Tyrannosaurs' domination of the globe might have been total
had it not been for a strange quirk in the arrangement of the continents.
75 million years ago,
the planet had a clear north-south divide,
with no physical link between the parts of the globe.
It meant the Tyrannosaurs couldn't spread to the southern continents.
Here, a different type of killer reigned supreme.
These were Abelisaurids.
In the last 10 years, Madagascar has provided
the most comprehensive evidence about these predators.
70 million years ago, Madagascar was already an island.
In the Cretaceous period,
Madagascar was subject to devastating droughts.
For big predators like Majungasaurus,
scavenging is the only way to survive.
(INSECTS BUZZING)
We thought Majungasaurus was the top predator here.
But then in 2003, some bones of a number of Majungasaurs
were reported gouged with teeth marks.
It appeared there was a bigger, more brutal killer at large.
(SQUAWKING)
(GROWLING)
(ROARING)
A carcass will attract every big predator for miles around.
(GROWLING)
A male Majungasaurus.
It is more than capable of challenging for the carcass.
(ROARING)
This fight is about more than just winning the feeding rights to a carcass.
When the bite marks on the mauled Majungasaurus remains
were studied more closely,
the marks on the bones were found to match
the only large carnivore in the region,
Majungasaurus itself.
This is the first irrefutable evidence of dinosaur cannibalism.
It might seem shocking, but it's a behaviour that clearly shows
the most successful killers will exploit any situation
to their maximum advantage.
Killer dinosaurs' ability to adapt was exceptional.
It meant they were able to colonise every continent on the planet,
continually evolving and changing.
Their dominance of life on Earth was absolute.
Yet they were doomed.
Their downfall was caused by an asteroid smashing into the Earth.
Travelling 20 times faster than a speeding bullet,
15 kilometres across,
it slammed into the Gulf of Mexico.
The impact released more energy than a billion atomic bombs.
The initial impact triggered wildfires, massive earthquakes and tsunamis.
But most devastating was the material blasted high into the atmosphere.
This shrouded the planet in a cloak of darkness that lasted for months,
cutting off sunlight.
The Earth was thrown into almost permanent night.
Animals that survived the blast
were now faced with their greatest ordeal,
as a devastating chain of events was set in motion.
Deprived of light, many plants died.
Plant eaters are the first to be affected.
Fresh growth of plants offers a glimmer of hope,
allowing the smallest to scratch out a living.
But these aren't enough to sustain anything for long.
(SCREECHING)
Scavengers initially have an easier time of it.
(SQUAWKING)
But this surplus is an illusion.
Once gone, scavengers will starve, too.
The impact resulted in the collapse of whole food chains.
And the extinction didn’t just affect dinosaurs.
Virtually all life on Earth was affected.
More than 60% of all species were wiped out.
Yet the extinction wasn't a lottery.
One factor more than any other determined the dinosaurs' fate:
size.
On land, no animal weighing more than 25 kilograms survived.
There just isn't enough food to sustain large animals.
Ironically, it's the very thing that makes dinosaurs so iconic
that condemns them to extinction.