Planet Dinosaur: Ultimate Killers Page #2

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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

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