Original subtitles

'Dinosaurs. Prehistoric monsters.

'Huge. Terrifying.

'I've always loved them. Always been fascinated by them.

'What's mind-boggling

'is that these extraordinary creatures

'roamed where we walk today.

'But what if I could go back in time,

'millions of years into the past,

'to the magical, dangerous world they lived in?

'I wonder, what would I make of them?

'Face to face.'

Oh, you can just pull up here.

Thanks.

Imagine being able to explore their world

and move with them. HE CHUCKLES

It's just a dream, I suppose, but...

Well, I must get on with my life.

Mind you...

You never know.

ROARS

For 180 million years, dinosaurs dominated our planet.

In this series, I'm going to be transported back

to the different eras of these awe-inspiring creatures.

To immerse myself in their amazing, magical world.

Hey! Don't do that!

With the help of experts

and the latest scientific discoveries from our time,

we'll put their power and strength to the test.

Unravel their remarkable story

from humble origins of the dawn of the dinosaurs

to see how they evolved a dazzling and bizarre array of forms.

To become giants.

ROARS

And produce some of the scariest predators

ever to have stalked the Earth.

Until their ultimate demise,

wiped from the face of the planet

in a single catastrophe of unimaginable power.

Come with me, as I travel back in time

to encounter the dinosaur.

For millions of years, dinosaurs ruled the Earth.

And during their reign, shifting continents and changing climates

allowed many different species to evolve.

Last time, I was in the Cretaceous,

one of the hottest times in the history of life on Earth.

The climate was ten degrees warmer than today.

The perfect conditions for the infamous raptors

to hunt giant grazers, like Iguanodontes.

Tonight, I'm coming closer to home,

to a period near the end of the dinosaurs' reign.

And they've saved their A-listers for last.

ROARS

For this period is ruled over

by some of the most chilling, awe-inspiring, and enigmatic animals

that have ever lived.

We've arrived at a key stage in dinosaur history,

the moment that evolution produces

the most terrifying killer ever to stalk the Earth.

It's 68 million years ago.

We're in the era known as the Late Cretaceous.

The dinosaurs' reign still has another two million years to run.

They are thriving.

This landscape around me

is a place you might nowadays call North America.

And if you look carefully enough,

this world is starting to appear a little more familiar than before.

Flowering plants have taken over,

fuelling an explosion in insect life.

And amid the conifers,

we can see trees that we'd know today,

like maples and oaks.

So much for the plant life,

but the animals of this age are far from familiar.

Oh, and look, there, at the water.

One of the most iconic species of the era.

The magnificent three-horned Triceratops.

There's a group of them enjoying a pause for some water.

And over there, that extraordinary-looking creature

is not actually a dinosaur at all,

but one of their flying cousins known as a pterosaur.

They look so ungainly, don't they?

Carting around those huge wings made of skin.

But if you were to see one in... There, like that, there!

See? They're so graceful when they're in the air.

ROARS

Something's spooked them.

And I don't think it's me.

LOW GROWLING

ROARS

This is the most fearsome dinosaur of them all,

the Tyrannosaurus rex.

Its name, actually, is doubly royal.

"Tyrannus" is Greek for king, and "rex" is Latin for king.

You have to say, he really does look

very much like the ruler of this place.

A truly formidable beast.

It's 12 metres in length and four metres in height,

and weighs in at eight tonnes.

ROARS

He's basically a double-decker bus on legs.

But with sharper teeth.

The product of millions of years of evolution.

But at just 68 million years BC,

he actually lives closer in time to the iPhone

than he does to the Diplodocuses of the Jurassic era.

Since their time, a quarter of a billion years in the past,

the giant supercontinent of Pangea has been gradually splitting apart.

As it split,

it isolated distinct populations of dinosaurs

in different corners of the world.

And it's this isolation that allowed them to diversify.

In what is today China,

68 million years ago, we find the feathered and beaked Oviraptor.

In Russia, the Olorotitan ruled, with its colourful head crest.

And in South America, the giant Argentinosaurus.

Weighing up to 100 tonnes,

it's one of the largest animals the world has ever seen.

T. rex fossils have only ever been found

in what is now North America.

At the time, the continent itself was split in half

by a vast inland sea.

And it's on the western island where our T. rex lives.

And it is not on its own.

Slightly terrifyingly, it's estimated

that at any one given time,

20,000 of these T. rexes were roaming around.

That means that over 2.5 billion T. rexes

once walked the Earth.

That's roughly the population

of Europe, North America, and Africa combined.

Let's take a careful look, shall we?

HE GIGGLES Those arms are frankly tiny.

They look really silly. I wonder what they're for.

ROARS

All right, all right.

Clearly touched a nerve there.

I should imagine those huge hind legs do most of the shifting around.

And they also act as a kind of a balancing point

between the bulk of the body and that huge sweeping tail.

And then there's the extraordinary head.

Just packed with teeth,

which I can imagine would do a serious amount of damage.

But there is something rather curious about those teeth.

If we compare him

to our Jurassic era predator the Allosaurus,

those teeth are really thin and sharp,

perfect for slicing through meat, like steak knives.

They were ideal for gouging out great lumps of flesh

like a meat cleaver,

thanks to Allosaurus' amazing gaping mouth.

But T. rexes are much thicker and rounder,

ideal for heavy-duty crunching.

It's clearly evolved to eat meat,

with its piercing teeth and strong jaws.

Which raises a question.

Was he better suited not for killing live prey

but for feeding off dead bodies?

Clues could lie in the modern-day cousins of Tyrannosaurus,

vultures.

Vultures rely on strong, dexterous muscles in their necks

when they tear flesh off bone.

The same muscles are found in our T. rex.

And they're not the only similarity.

Vultures and T. rex also have an S shape to their necks,

which provides leverage

when ripping back to tear off chunks of meat.

They also share sharp versatile talons

to grip on their prey.

So, it seems our king of beasts was perfectly built for scavenging.

But really, was T. rex not the hunter/killer

certain movies have led us to believe?

To help me find out is one of the world's leading dinosaur experts,

Dr David Hone, from Queen Mary University of London.

Hello, David.

My good... Oh, dear, oh, dear.

Mind you, none of us look our best

when we're tearing into our dinners, do we?

I mean, this is a dead Triceratops. So it's scavenging? Yes.

That's not very regal.

They are scavengers, but they were also predators, too.

So, like almost all large carnivores,

they were killing things actively

as well as taking whatever was available if they found it.

And of course, so many modern species

are both predators and scavengers.

So, hyenas are always the skulking scavenger,

but actually, they predate most of their prey.

And people think of lions as the king of beasts,

that kills everything,

and actually, they're very adept at stealing food off hyenas.

Tyrannosaurs and Tyrannosaurus has particularly strong, thick teeth,

and an extremely powerful bite,

and they're capable of biting through even very thick bone.

But actually, at the front, they have this little row

of actually very small and flattened teeth,

and what they're actually doing

is a form of feeding called scrape feeding.

They're literally pushing the teeth down onto the bone and pulling back.

Yes, we've got some evidence of that on a fossilised Triceratops bone,

where you can see bite marks left by a scavenging Tyrannosaur.

We find these long rows of parallel stripes,

only on areas where the muscles attach to bone.

So they're very carefully feeding on just some areas,

and just stripping the muscle off to eat it.

Oh, I've done that!

We do it with biscuits. Yeah. Take the top off and scrape it away.

Exactly what they're doing. My heavens.

T. rex is clearly an expert scavenger,

skilled at husking meat from bone.

But he is undoubtedly interested in live flesh, too.

And if I hang around long enough, we might be able to see

just what kind of a hunter T. rex is.

I've travelled back in time to a magical and mysterious world,

on the western shores of a vast inland sea

in a place you'd call today North America.

Home to some of the most iconic dinosaurs of all time.

We're in the Late Cretaceous period,

and we've been on the trail of the most feared predator, T. rex.

This one has been scavenging an old carcass,

but just now, he's picked up the scent

of something far more appetising.

Fresh meat.

This is one of the flying cousins of the dinosaurs, a pterosaur.

No doubt there's plenty of juicy meat on those flying muscles.

ROARS

Ha! What an incredible sight.

That was Quetzalcoatlus, the largest ever of the pterosaurs.

He may have looked a bit ungainly on the ground,

but once he took to the air, it was like a small plane,

and about the same size, too.

Pterosaurs like this

lived alongside the dinosaurs throughout their history.

But the mystery is, how did they cheat gravity

and take to the air like that?

To answer that, we'll have to travel even further back in time.

170 million years ago, in the late Jurassic period,

the Isle of Skye, off the west coast of Scotland,

was a warm, tropical land, dotted with lagoons.

Scroll forward to the present,

and a team from Edinburgh University,

led by American palaeontologist Professor Steve Brusatte,

made a record-breaking discovery.

It was right here on this stretch of coast on the Isle of Skye

where we found Dearc, the new species of pterosaur.

One of our students noticed a jawbone and some teeth

protruding from that rock.

We took a look, and we saw there was actually an entire head in there.

And then, when we started to take it out of the rock,

we realised that head connected to a neck,

and connected to a body, and connected to a skeleton.

Steve took that skeleton back to the lab.

And it turned out to be something very special indeed.

The fossil of a 170-million-year-old flying monster.

The largest Jurassic pterosaur ever found.

This is a really important fossil.

I think it is a crown jewel fossil for us here in Scotland.

It's not just a beautiful fossil.

Because it happens to be one of the only really good pterosaur skeletons

from the middle part of the Jurassic anywhere in the world.

Microscopic analysis revealed this creature

to have not yet fully grown,

but it was already enormous.

There's one wing.

And here is the other, more complete wing.

We have the upper arm bone, the forearm bones.

And so if both wings were stretched out,

this wingspan would have been something like 2.5 metres.

And that's wider than a king-size bed.

Steve's discovery shows the giants of the sky

were around millions of years earlier than first thought.

Up until we found this fossil,

we used to think that pterosaurs never reached those sizes

until tens of millions of years later in the Cretaceous period.

The fossil even revealed a secret as to how they flew.

A secret that can be counted on just one finger.

I think the most beautiful part of the fossil is the little hand.

And we have three little fingers.

Each one has a very sharp hooked claw on the end.

And then a much bigger fourth finger, the ring finger.

And it's that one finger that anchored the wing.

And the wings of pterosaurs were a giant sail of skin.

So very different from the wings of birds or bats.

Modern-day birds have wings with feathers attached to bones.

Bats' four limbs form webbed wings,

and to fly, they flap all four spread-out fingers.

But the pterosaur used just that extended ring finger,

acting as a mast,

that stretched along the leading edge of the wing.

And that finger holds the answer

to how anything so massive could stay in the air.

If I were to look at my ring finger, say in an x-ray,

it would be really solid inside.

But not pterosaurs.

The bone is basically hollow.

You can see the walls of bone are pretty thin,

and the middle would have just been completely full of air.

And in fact, that's true of almost the entire pterosaur skeleton.

These animals were big, but they were featherweight,

and that helped them stay aloft when they were flying.

So, hollow bones allowed pterosaurs to keep their weight down,

and grow large,

and they continued to grow in size right up to the time I'm now in,

in the Late Cretaceous.

By then, Quetzalcoatlus, a pterosaur the height of a giraffe,

had become the largest animal that has ever taken to the skies.

So, Quetzalcoatlus is one of the most extraordinary animals

that has ever evolved

in the entire 4.5 billion year history of the Earth.

This was a reptile that was the size of a fighter jet.

Its wingspan was over ten metres wide.

It's the biggest thing that has ever flown

in the entire history of life, as far as we know.

I mean, you'd have to say,

that is so impressive when it's on the ground as well.

I mean, it's huge.

I believe 20 feet, something like that?

About the size of a giraffe in height?Yep.

Amazing creature. Absolutely extraordinary.

But how does something like that actually take off?

First of all, an animal this size

is actually only in the realms of 250, 300 kilos.

Enormous, but a giraffe that size is a tonne.

So not that heavy, for that wingspan.

And secondly, birds take off with their legs.

So they actually jump with their legs, and then start flapping.

So it's a spring? Yes.

But they're gonna take off with just their forelimbs.

Their wing muscles, which they already use for flapping,

and are therefore extremely strong,

it's gonna use to launch off the ground.

So it's jumping with its big muscles.

Let's see if I can make it show us.

HE CLAPS Fly, my pretty!

CLAPPING

Well, that's what I call a successful take-off.

Extraordinary.

Well, it seems our T. rex didn't have much chance

of catching our Quetzalcoatlus.

And to be honest, it wouldn't really have been a fair fight, anyway.

But T. rex wasn't the only predator around the world at this time,

and each was supremely built for its own choice of prey.

In prehistoric North Africa,

Spinosaurus uses its long snout to pluck fish from coastal shores.

In ancient Mongolia,

Saurornithoides has excellent eyesight

to spot small mammals scurrying around in its desert home.

And in Argentina, Mapusaurus hunted massive sauropods

in wide-open plains by working together in packs.

And here in North America,

our T. rex is eyeing up something a little more grounded.

A juicy Triceratops.

At least it can't take flight and escape into the air.

Even so, to track down, catch,

and kill one of these armoured beasts

is going to be far from easy.

So, how did T. rex choose its prey?

That is something Professor Roger Benson of Oxford University

is trying to find out.

He's going inside the mind of a very famous T. rex called Stan

to get a sense of how it sensed the world around it.

Stan was excavated in 1992 from South Dakota, in America.

His bones were sold in 2020 for an eye-watering $32 million.

Making Stan not just the best-preserved T. rex ever found,

but the most expensive dinosaur in the world.

This is a full-sized replica of Stan's skull.

One of the things I'm really interested in

is how we can use information from the bones

to understand the sense organs of this animal.

Sense organs don't fossilise well,

so Roger has just the skull to study for clues

as to how T. rex might have used its sight, hearing, and smell.

This is the eye socket.

About five times as wide as a human socket.

And it could have housed a potentially massive eyeball.

An eye socket of this size has potential

to give T. rex really excellent vision.

And one of the interesting features of the eye sockets of T. rex...

As you can see, the skull is wide at the back,

it's narrow at the front.

And what this means is that the eye would have looked slightly forwards,

allowing it to focus on things straight ahead of it,

and get some idea of depth.

And what that might tell us is that T. rex might have been

a relatively effective visual predator.

So it had good eyesight.

But what other super sense could help Stan hunt?

Clues could lie in the animal's brain.

So, Roger scanned the inside of Stan's skull

and used a state-of-the-art 3D printer

to build a life-size, three-dimensional

replica Tyrannosaur brain.

It looks like a kind of wacky alien spider,

but in fact, all of these structures coming out of the side,

those are nerves, blood vessels,

and other structures that emerge from around the brain.

It may be small, but this life-sized model brain

can shed light on how T. rex sensed the world around it.

That way is forwards, towards the snout.

That way is backwards, towards the neck.

And one of the structures we find at the front

are the olfactory bulbs,

the part of the brain that processes information on smell.

And there's really no predatory dinosaur

that has proportionately bigger olfactory bulb than T. rex itself.

Which means T. rex had the best sense of smell

of any dinosaur yet discovered.

And acute 20/20 forward-facing vision.

All the super senses needed to see or sniff out prey,

day or night.

Which raises the question, was T. rex - this fearsome predator -

actually a night-time hunter?

Well, one thing you can say about the Late Cretaceous

is there's no spill pollution

from street lighting or big cities, is there?

But let's, erm... Let's add our own light.

There. Now...

Whoa.

LOW GROWLING

There he is. Look at that.

And these super senses they have,

they lead you to believe that maybe he was nocturnal?

Yeah. I mean, that's one thing that's really gonna help.

You don't need amazing eyesight in the daylight.

Our eyesight's pretty good,

and yet their eyes are massively bigger,

so they would operate very well at night.

And then on top of that,

it's very hard to hide an animal of this size.

I see what you mean. So they're better disguised at night?Yeah.

So it's got a superior sense of smell?

Yeah. A very good sense of smell.

Again, that's useful in daylight,

but it's gonna be more useful at night when you can't see that far.

Yeah. So again, we don't know for sure,

but it indicates that it could well be good in the darkness.

And as for their colouring, do you think that's dark?

Well, those dark black stripes on the body

would really help break up the outline in low-light conditions.

So a bit like a zebra?

Or, indeed, like a leopard,

or any sort of animal with some kind of marking?

Spots and dapples, yeah.

Using shadow and highlights to disguise its outline.

It's extraordinary, isn't it?

I don't really think it's much of a kind of stealth creature.

No, it never will be. But an incremental advantage,

if it allows you to get ten metres closer,

that could be the difference between getting a meal and not.

Then you spring and you pounce. Yeah.

Well, before he springs and pounces on us,

I'm gonna turn the light down.

Ooh, I think he's found a target.

He may have the element of surprise.

But does he have the pace to run down his prey?

ROARING

I'm in the Cretaceous period,

on a nocturnal hunt

with one of the most fearsome predators of all time.

T. rex is equipped with fantastic senses

to help him navigate at night.

Smell, hearing, and eyesight.

And with a bulk like that, darkness is the perfect cover.

He's found a likely target over there,

a juicy-looking Triceratops.

But will he be quick enough to catch his prey?

In fact, how can we possibly know how fast this,

the largest animal ever on two legs, could really move?

Evidence may lie with a distant descendant

of this king of dinosaurs,

the ostrich.

And they do have a surprising likeness.

This is an ostrich foot.

This is a Tyrannosaurus rex foot.

They're very, very similar. If we take the ostrich toe bone

and hold it next to the same bone in T. rex,

you can see just how similar they are.

The feet are fundamentally built out of the same building blocks.

Palaeontologist Dr Peter Falkingham of Liverpool John Moores University

is an expert on dinosaur locomotion.

To him, the key to understanding how fast they could run

lies in how they support their weight in the first place.

ROARS

So one of the first things you can see here

is that the T. rex bone,

while it's almost the same shape as the ostrich bone,

one difference is this divot on the T. rex bone.

And that's where the tendons would have attached.

And those tendons would help brace the toe,

absorb impacts from the large mass of the T. rex.

So, shock-absorbing ligaments for support.

But what about moving?

With a top speed of 70 kilometres per hour,

greater than a racehorse,

the ostrich is the fastest and largest two-legged animal

alive today.

To understand how they run, Peter films them in ultrahigh speed.

I'll be able to look at really fast motion

and slow it down and be able to really quantify the motion.

You can see both feet are off the ground at the same time.

That means it's a run, not a walk.

And we can pause that.

And if we start tracking, it will follow that.

And you can see quite clearly as it's pushing off,

that limb is very, very straight.

For an ostrich to support its weight when running,

it keeps its legs as straight as possible,

and positioned directly under the main mass of its body.

So, what you can see as the video plays

is that the ostrich is swinging its leg from the knee.

Now, an ostrich is about 100 kilos.

A T. rex is eight tonnes.

So that's really gonna have to try

and keep its limbs as straight as it can to support its weight.

By applying these ostrich data to a computer model,

Peter can simulate how T. rex ran, too.

So this model is showing reconstructed muscle positions

on T. rex's skeleton.

And you fire those muscles,

and you figure out how the bones must have moved

to support the weight.

So you can see the feet, they're barely off the ground together,

so it's only just a run.

And you can see that the legs are straight.

They're straighter than the ostrich.

T. rex really is pushing the limits of how large you can get

and still support yourself on two legs.

So it's no surprise that it's finding it difficult to run fast.

So, how fast could T. rex go?

ten, 15, 20 miles an hour, tops.

For comparison, an Olympic sprinter would be 27 miles an hour.

So it's not as fast as the fastest human,

but it's probably faster than me.

It looks like we might be about to see that running speed in action.

Our T. rex is on high alert.

He's spotted a lone Triceratops over there.

This could be an opportunity to see how fast he can go.

And I've asked dinosaur expert David Hone

to provide a post-match analysis of how the hunt goes down.

ROARING

STEPHEN CHUCKLES

Well, a successful kill.

What were the tactics it uses there against the Triceratops?

So it's gonna get in as close as it can.

Though as we said, it's pretty difficult at that kind of size.

But once it starts going, basically, it's relying on distance.

It's better over long distances

than pretty much anything else that's out there.Oh.

And that's the usual way?

It's not about speed, like a lion or a cheetah or something?

Yeah. They're not that fast.

I mean, animals at this kind of scale...

It looks pretty quick, cos of the size of them,

but they're not as fast as you would think

for an animal that's an active hunter.

But again, the scale of everything,

the prey is relatively big and slow as well.

And then when they get close,

obviously they're mostly striking from behind anyway.

Yeah, it went for the back of the animal.Yeah.

So, dinosaurs have, basically,

most of their big leg muscles

go from about halfway down the thigh to about halfway down the tail.

So that area is a single giant block of muscle.

So any kind of bite in there

is immediately gonna cripple it and stop it running.

But also, the blood loss and shock, and the rest of it,

is going to be... Not fatal, but it's not going anywhere.

So it rips into the sort of rump of the Triceratops? Yeah.

Brought it down.

It's game over pretty much at that point.

We've actually got some more evidence here

that T. rex has been feeding.

And, indeed, going past afterwards.

What on Earth! Well, it's what you think it is.

It is, I'm going to use the word, a turd.

It is. Erm... This is what they produce.

And this is a genuine one?

It's not just a made-up idea, is it?

I mean, obviously it's not the real...

But is it like fossilised poo? Yeah, it's based on one.

And actually, inset are broken bit of bone from a young dinosaur,

which is what we found in Tyrannosaur,

preserved Tyrannosaur coprolites.

Oh, so it would crunch up on babies?

On junior? They would indeed.

Mostly what they're eating is youngsters.

But we can actually learn some stuff about it from this,

because the very fact that the bone has passed through,

if you looked at something like a crocodile,

bone comes out almost as a slurry.

The acid is so strong that the bone basically dissolves.

It doesn't here.

And it's been through a much bigger animal.

So its digestive power is not some kind of...

It's not some kind of superpower,

which I think some people think it is.

It's a simpler tube, really? Yeah.

But it's just going for a more normal digestion,

rather than a super bone eater.

So again, that harks back

to it not being some kind of specialist scavenger

that can dissolve bone and get every last bit out of it.

Cos even the bones of babies come through.

I think we've learned what we can from this. I'll pop it back.

Do that. Pop the turd back, if you'd be so kind.

And then wash my hands. Yeah!

So, we've amassed some terrifying examples

of the power of those T. rex jaws,

crunching through the bone of a Triceratops.

And passing the remains of baby dinosaurs in its waste.

But what would it be like to be on the receiving end of that bite?

The crocodile has the most powerful bite of any animal alive today.

Its over 1.5-tonne nip is powerful enough to crush a human skull.

But how strong was T. rex's bite

compared to today's world record-holder?

To find out, T. rex's fearsome jaws are being brought back to life

with this mechanical replica.

Capable of exerting the same force as a T. rex jaw.

Operated by University College London engineer

and dinosaur enthusiast Dr Adam Wojcik,

and paleobiologist Andre Rowe.

I'm a big T. rex guy.

I've been studying a lot of bite forces.

And T. rex's highest bite forces

were generally around four times as much

as the largest modern crocodiles.

Which is quite scary, when you think about it.

And obviously it's going through a whole array of teeth,

you've probably got around about 250kg of force per tooth.

A T. rex could channel five tonnes of pressure through its teeth.

Now,that's gonna be pretty destructive.

First up in that t. rex jaw press, a cow skull.

CRACKING

Fantastic.

The bone has definitely exploded.

It's kind of split.

You heard the noise there. Quite the crack.

I have no doubt that T. rex could have done this

to a large herbivorous dinosaur back in its heyday.

And probably a lot more as well.

Yeah, no doubt about that.

The bone is destroyed.

But this doesn't come close to what a real T. rex was capable of.

I think the next thing for us to do

is test it on something a little bit more chunky.

Without any dinosaur bodies available to test today,

we're going to try something designed to withstand being crushed.

Andre, do you think on the basis of this experiment,

T. rex could actually have chewed its way through a brick?

Well, considering the bite forces,

and the evidence we have from our tests today,

I don't think that it's outside of the question...Right.

..if we somehow brought bricks back to the Late Cretaceous.

It would be quite a spectacle, that's for sure.

Well, I've discovered this incredible statistic

about its bite force,

that it's the greatest of any animal that ever lived on Earth.

Kind of overengineered.

Because you're talking about the ability to crush bricks.

All it needs is a bone.

And these are avian bones, some of them are hollow.

Some of them. But a lot of the herbivores don't have that.

And so, of course, for the big things like Triceratops,

if you want to break into them,

or break up the carcass to be able to consume it,

then you're going to need a comparable bite power

to get through the bones of a huge animal.

ROARS

Ah, there's a second T. rex approaching.

This could get interesting.

ROARS

I'm in a time near the end of the dinosaurs' reign.

I've already seen the scavenging ability of our mighty T. rex.

And witnessed an incredible fight with a Triceratops.

But it doesn't seem to be alone in this prehistoric wilderness.

An outsider has just arrived here in the Late Cretaceous period.

At first, I thought he was gonna fight our T. rex

over its fresh kill.

But now... THEY ROAR

..I'm not so sure.

Because this dinosaur is, in fact, a she.

Maybe we're about to witness the more loving side of T. rex.

A bit of Tyrannosaurus sex, if you like.

ROARS

Well, that was quick.

I wonder if dinosaur expert David Hone

can shed any more light on how we can possibly know anything

about how Tyrannosaurs really mated.

Well, they can't be accused of wasting time over the matter,

can they? No, definitely not.

But that's pretty common.

A lot of modern animals

take seconds, really, for this kind of thing.

We saw a bit of sort of muzzling and nuzzling.

Do you think that was likely? That they would rub their noses?

Most animals go through some form of courtship ritual,

even if it is only a few seconds.

And we do at least have plenty of birds

that go in for beak rubbing and things like this.

There's even been a specific suggestion

that Tyrannosaurs did this with very sensitive lips.

That's a nice thought.

I suppose I can't help mentioning that,

with all dinosaur coupling, you feel the sheer size.

I mean, can the female take the weight?

Well, presumably she would,

otherwise we wouldn't have had dinosaurs for 160 million years!

I wonder if the T. rex as well,

those tiny hands, are they enough to help him cling on, as it were?

I'm sure they helped a little bit,

but I doubt that's what the arms were functioning for.

Because otherwise the females probably wouldn't have had them.

And now?

Do they stay together and raise their young as a couple?

Very probably. It's likely that Mum at least,

and quite possibly both,

were engaged in looking after the babies after they hatched.

As well as looking after the eggs,

and guarding the nest in the beginning.

Well, these two seem to be getting on very well.

But when it comes to T. rexes, that isn't always the case.

Dr David Gelsthorpe at the Manchester Museum

is examining the full-size replica of Stan,

the most complete and valuable dinosaur yet discovered,

for clues as to just how violent life was for this king of beasts.

Stan probably wasn't fully grown.

He was probably about 20 or 30 years old.

He may be a youngster,

yet Stan bears marks of how dangerous life was

in the Cretaceous.

There's a hole just up there.

It's quite a round circular hole.

I've got a T. rex tooth.

And if you hold it up next to the hole, it fits perfectly.

So this is really great evidence

for another T. rex having an encounter with Stan,

and the tooth going so far in

that it's actually made this puncture wound in the scalp.

And there's more evidence of sparring

further down the skeleton, too.

On the third vertebra back,

there's quite a sort of bulbous knobbly piece of bone,

where the T. rex has had some kind of injury.

The bone has grown around this injury.

It very likely is evidence of a fight.

There probably would have been bigger and more aggressive T. rexes

that were right at the top of the food chain.

But he no doubt would have been challenging his way to the top.

And our T. rex has been in a few fights, too.

There are scars all over his body,

showing that, well, he may be a mean, killing machine,

but he faces his own dangers.

In the next episode,

we're going to see how T. rex faced threats from the plant eaters,

as creatures like Triceratops used their formidable defences...

..to fight back.

And as these creatures enjoy the heyday of the Late Cretaceous,

they are completely oblivious to a warning sign in the sky.

That bright star is, in fact, an asteroid.

And the extinction of the dinosaurs

is hurtling towards a devastating collision

which will change the course of the history of life on planet Earth.