(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 1 1-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,
1 50 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 thisJurassic 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 1 5 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 1 54 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.
Microraptor.
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,
1 5 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)
(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.