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NARRATOR: Before
humans ruled the world,

planet Earth was
a land of giants.

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Snakes the length of buses.

JASON: I am still to
this day completely
amazed by this animal.

NARRATOR: Ocean killers
with jaws big enough to
swallow a person whole.

HUBER: These jaws were able to
rip out this big chunk of car.

NARRATOR: And predators
that dwarf T-Rex.

PAUL: We're talking something
of enormous length that could

slice you with one motion.

NARRATOR: But, of all the
creatures that have ever lived,

which is the biggest?

Using the latest discoveries
and cutting edge science,

we're going to reveal a top
ten of the biggest beasts ever

that have walked the earth,

swum the seas and
soared the skies.

MIKE (off-screen):
This is awesome!

NARRATOR: Analyzing the
ultimate giant beasts across

the animal kingdom,
species by species,

and using length as
our ultimate guide,

we countdown from ten.

And first on our list is a
creature you'd never expect,

a terrifying beast,

the biggest insect
that ever lived.

Long before the dinosaurs,

a winged giant
terrorized the skies.

Flying at over
20 miles per hour,

and with jaws that could cut
small reptiles to pieces,

its common name
is the griffinfly.

A clue to this ancient mega
bug was discovered in 1940 in

Noble County, Oklahoma, in
the southern United States.

Today, it's the job of insect
expert Brian Farrell to take

care of that clue,

a fragile fossil that's
275 million years old.

BRIAN: This really is
a spectacular fossil.

NARRATOR: This fossil
is the largest insect
wing ever discovered.

BRIAN: To get an idea of
just how big this insect was.

This is a reasonably
large sized modern
dragonfly for comparison.

It's about one fifth
the size, at most,

of this meganeuropsis.

NARRATOR: Looking
at this single wing,

it's clear just how big
the griffinfly could get.

It had four wings,

the biggest pair spanning
two and a half feet across,

that makes it six times larger
than many modern dragonflies.

If it was around today, it
would be a match for a hawk,

and span the outstretched
arm of a six foot man.

From smaller but more
complete fossils,

experts have discovered that
griffinflies didn't merely

look like today's dragonflies,

their anatomy was
incredibly similar.

So it's likely that they
behave the same way too,

as deadly hunters.

Anthony Leonardo is a world
expert in dragonfly flight.

He's unlocking the secrets of
what's makes these flying aces

such expert killer beasts.

They have four wings that
can beat independently.

ANTHONY: If you look
at the wings closely,

you can see that
they're quite amazing.

The dragonfly can fly
forwards, backwards,

upside down.

It can also pull these
incredibly sharp 6G turns.

NARRATOR: They also
have eyes with virtually
360 degree vision,

powerful legs for grabbing
insect prey, and killer jaws.

ANTHONY (off-screen):
They have these massive
mandibles and these kind of

pinching crunchers, and they
very quickly cut and slice all

this prey up into little bits
that the animal then swallows.

NARRATOR: But how did the
griffinfly get so big,

and why are modern
dragonflies so much smaller?

The answer lies in the way
all other insects breathe.

ANTHONY (off-screen):
Insects don't have lungs.

On the outside of the
dragonfly's body are little

openings called spiracles, and
these are little holes that

open and close, and they
basically are little pumps

letting air into the
dragonfly's body and then

pushing it back out.

NARRATOR: Once
through the spiracles,

the air moves through a
network of tubes called trachea.

This way, oxygen is fed
directly to every single

cell of the body.

The problem is, there
are so many tubes there's
little room left for muscle,

and that's what stops today's
dragonflies getting any larger.

So how did they ever
reach the monstrous
size of the griffinfly?

How did they pack enough
muscle into their bodies to

power giant wings?

One paleobiologist at
Midwestern University,

John Vandenbrooks believes
he has the answer.

He's doing experiments to
uncover the secrets to what

makes a bigger bug.

John thinks that growing
bigger was all down to the

amount of oxygen in
the air they breathed.

JOHN: Oxygen was much
higher in the past.

Today oxygen's about 21% of
the atmosphere around you.

In the past it
was as high as 31%.

NARRATOR: An extra 10%
might not sound like much,

but that's 50% more oxygen
than we breathe today.

JOHN: So perhaps that increase
in oxygen in the atmosphere is

what led the possibility that
those insects could get as

large as they did.

NARRATOR: To investigate,
John decided to do
something radical.

change the oxygen the
bugs could breathe.

First, he takes cockroaches
and breeds them at far lower

levels of oxygen than today.

JOHN: In this top chamber, we
have cockroaches reared under

lower oxygen levels, about 12%,

and you can see how
large this individual is.

NARRATOR: It may look
large, but it's actually
small for the species.

John then rears other
roaches at the oxygen
levels of the past.

JOHN: Comparatively, the
cockroaches reared down here

are being reared in a high
oxygen level of about 31%

and you can see now
how large this individual is,

much, much larger than
those reared at the
lower oxygen levels.

And it's even more pronounced
if we're able to compare the
two animals.

NARRATOR: The results are
clear and astonishing.

More oxygen means bugs can
have a smaller internal

breathing system.

JOHN (off-screen): We
can now definitively say,

as oxygen goes up that it
actually allows for the animal

to put more things
inside its body,

so it can have more muscle
and it can become one of these

really large, vicious
predators that we see

300 million years ago.

NARRATOR: Had we been
around to witness it,

the griffinfly would have
been a truly terrifying sight.

This was the biggest insect
ever to fly Earth's skies,

but our next beast
is far, far bigger.

Fast forward from griffinfly
to 27 million years ago.

Then the skies were ruled
by a feathered giant.

With wings as wide as
a two lane highway,

and a cruise speed
faster than Usain Bolt,

it could travel to every
corner of the planet.

(cawing).

The evidence of this giant
first came to light in
South Carolina in the USA.

In 2010, paleontologist Dan
Ksepka discovered a collection

of bones in a storeroom
at the Charleston Museum.

KSEPKA (off-screen):
When we pulled open the
drawer and I saw this for

the first time it was just
absolutely spectacular.

NARRATOR: Laying
the bones out,

Dan could see this
was no ordinary find.

KSEPKA (off-screen):
It has this skull with
these bony toothed jaw

that almost looks
like a crocodile.

NARRATOR: But it wasn't
any kind of reptile.

What Dan had discovered
was the largest flying
bird of all time,

a new species they
called pelagornis sandersi.

KSEPKA (off-screen):
This massive element
here is the humerus.

This is the first bone
of the wing skeleton,

so it's equivalent
to the upper arm bone
in a human skeleton.

This bone, in particular, is
longer than my entire arm,

so we have a
remarkably long wing.

NARRATOR: The giant bird's
body was six feet long.

With a 24 feet wingspan, the
largest bird alive today,

the wandering albatross,

could fit easily under
one of its wings.

Pelagornis's wingspan rivaled
that of a Harrier Jump Jet.

Everything about the
skeleton tells us this
bird must have flown,

but how could something
this big possibly have
stayed airborne?

A closer look at the bones
provide Dan with a vital clue.

Like flying birds
today, its bones are
hollow and super thin.

KSEPKA: The bone wall is
about a millimeter thick,

and so this animal
would have been very
lightweight for its size.

There's less weight
to support in flight.

NARRATOR: It rivaled the
wingspan of a fighter jet,

but this giant bird
weighed only 48 pounds,

less than a third of the
weight of an adult human.

Light as it was, one
bone still casts doubt

on its ability to fly.

KSEPKA: This
bone, the scapula,

is the equivalent to our own
shoulder blade and you can

see it's, it's just so small.

It's actually almost comically
small and this certainly

reveals that this bird was
not a high powered flapper.

NARRATOR: If it wasn't
flapping its wings,

how did pelagornis fly?

Flight biomechanics
expert, Mike Habib,

believes the answer
lies with this.

MIKE: I'm out here to try hang
gliding for the first time.

I'm really excited.

I'm hoping this'll give me
some idea of what being a

pelagornis would be like.

NARRATOR: A hang
glider has a similar
wingspan to pelagornis.

It's also lightweight,
has a hollow,

tubular skeleton and
a large, rigid wing.

MIKE (off-screen): The
physics don't change,

so an airplane wing or
hang glider wing looks

fundamentally very
similar to an animal wing,

even though they're
made of different stuff.

NARRATOR: The only way
Mike, or pelagornis,

could get airborne would
be to run into the wind.

MIKE (off-screen):
Hoping that I, I run
properly and we launch and

I don't have to be one
of these people that gets

dragged along on their face.

MAN: Are you
ready to take off?

MIKE: Ready to take off, okay.

MIKE (off-screen):
This is awesome!

Ah man!

This is giving me a little bit
of a glimpse of what it would

be like to be a giant
flying animal in the past.

This is an amazing
feat of engineering,

and it's a great
way of soaring,

but pelagornis
did a lot better.

NARRATOR: 27
million years ago,

nature produced a glider that
was about four times more

efficient than
this hang glider.

In fact, pelagornis was a
better glider than anything

that has ever lived or that
technology has ever produced.

MIKE: So we were in the
air for a good ten minutes.

A nice long flight, but
pelagornis would have been

one of the champions
of long distance flight.

Probably could stay in the
air for weeks at a time,

maybe even months at a time.

NARRATOR: Staying aloft
for long periods was
essential for pelagornis.

Its bony teeth, ideal
for catching fish,

reveal it was a sea bird.

KSEPKA (off-screen): 27 million
years ago, pelagornis was living

in this open sea environment.

Pelagornis could probably
travel across thousands of

miles of ocean
without much thought.

NARRATOR: So how did
pelagornis manage such an

extraordinary feat?

Dan thinks the clue may lie
with the modern master of

ocean flight, the
wandering albatross.

Albatrosses make use of the
way air flowing over the oceans

can change speed.

They perform a daredevil
maneuver called dynamic soaring.

Dan believes, if pelagornis
was to survive out at sea,

it must have done
the same thing.

KSEPKA: So, if we
look at the waves,

the wind above the waves is
going more slowly than the

wind higher up, at a higher
altitude above the waves,

especially out
on the open seas,

and dynamic soaring birds can
use this to their advantage.

NARRATOR: They swoop down
to the ocean surface then

pull up at the last second.

Pulling up gives a bird
enough momentum to rise up

and catch faster
moving air currents.

Flying in loops like this,
pelagornis would have been

able to cover vast distances
and grab fish from the surface

whilst burning
very little energy.

This was the biggest and
most efficient flying bird

in the history of the planet.

It ruled the ocean skies.

Pelagornis was at the limit of
how big birds could grow and

still get into the air, but
if you think that's big,

coming up at number eight
is an absolute whopper!

NARRATOR: Imagine walking
into a modern zoo where they'd

somehow managed to
resurrect the largest
mammal to walk the earth.

What you'd see is this: 20
tons of hide bound flesh,

standing more than
two stories tall.

Evidence of this ancient
mega mammal emerged in the

20th century in what
is now Pakistan.

But today, this evidence
is far from Asia.

Paleontologist,
Mikael Fortelius,

is investigating an
extraordinary collection of

the beast's bones in London's
Natural History Museum.

MIKAEL: Easy.

NARRATOR: This colossal
skull is testimony to
its sheer size.

MIKAEL: The head sits
on a very long neck.

There's never been
anything similar to this.

NARRATOR: Put all
the bones together,

and you get something that
looks like a cross between

a giraffe and an elephant.

It's called paraceratherium.

It was so big a six
feet man could easily
fit between its legs.

It stood 25 feet high.

It was nearly twice as tall
and three times as heavy as

the biggest land mammal today,
the African elephant and,

at 26 feet from nose to tail,

it was as long as an
Abrams battle tank.

Now the obvious question has
to be, why did it get so big?

But there's an
added complication,

while some scientists believe
that paraceratherium lived in

thick forests, Mikael
Fortelius thinks this

creature's habitat was harsh,

afflicted by dry seasons when

water was scarce and
vegetation sparse.

How does an animal
become a giant when
food is in short supply?

Mikael Fortelius believes
the answer lies in the teeth.

MIKAEL: Looking at the teeth
will allow us to understand

why this animal
got so very large.

The teeth are worn in
a way that only happens

when you're eating leaves.

NARRATOR: And,
for eating leaves,

sheer height would give this
animal a massive advantage.

Like a giraffe, it could get
to food that's beyond the

reach of most animals.

So that explains
paraceratherium's height,

but not its massive bulk.

Fortelius believes that the
explanation for that can be

found in the harsh
environment itself,

that the animal grew big
because of, not in spite of,

its tough surroundings.

MIKAEL: If you're small, just
one day without water is a

terrible thing and may kill
you, but the larger you are,

the more buffered you are,
the more you can deal with

harshness in this sense.

You can go without
food, without water.

I think that's what was
driving the size increase.

NARRATOR: Not everyone agrees
with Fortelius's theory,

but there's no
doubt that, somehow,

paraceratherium thrived.

And it must have consumed
vast quantities of
vegetation every day.

To find enough food,
it needed to range over

hundreds of square miles.

And that may be the reason
for what is, perhaps,

the most remarkable thing
about this amazing animal,

its feet.

Biomechanics expert,
John Hutchinson, has analyzed

paraceratherium's
foot bones

and produced a 3D model.

He's struck by just how much
it resembles that of one of

today's giants:
the rhinoceros.

In fact, weighing in at
only one sixth of its size,

the rhino is paraceratherium's
closest living relative.

And Hutchinson's
research shows that,

in terms of size to weight,
its feet must bear the

heaviest loads.

HUTCHINSON: Rhinoceros, the
pressure of its feet are way

higher than in a horse,
a human, even an elephant.

Rhinos already today are
living at an extreme in
terms of foot pressure,

and paraceratherium
seems to have pushed
that extreme further.

NARRATOR: On the feet
of both the rhino and
its ancient cousin,

there are three
gigantic, hoof-like nails.

There's also a fatty
pad designed to act
as a shock absorber.

The paraceratherium's foot is
proportionally more slender

than a rhino's, meaning it
has to bear even more stress.

HUTCHINSON: My calculations
suggest that paraceratherium

might have borne as much as
50% more pressure on its

feet than a rhinoceros does.

NARRATOR: In fact, this was
the heaviest mammal ever to

walk the earth and John's
calculations suggest one

extraordinary fact.

HUTCHINSON: Paraceratherium
would have put more pressure

on its feet than an
average tank's treads
would put on the ground.

That's pretty staggering.

NARRATOR: This was the
biggest land mammal ever and,

with footsteps this heavy,
you'd have been well advised

to stay out of its path.

So far, on Top Ten
Biggest Beasts Ever,

we've met a deadly dragonfly
the size of a hawk,

a giant bird the
size of a plane,

and a mega mammal twice the
size of an African elephant.

But next up is an
even bigger beast

that could launch
into the skies.

♪ ♪

NARRATOR: This is the closest
Earth has ever got to a real

life winged dragon.

70 million years ago, while
the dinosaurs ruled the Earth,

the skies were
ruled by pterosaurs.

Their name means winged lizards,

and paleontologist, Gareth Dyke,

has spent more than ten years
of his life hunting them.

GARETH: Pterosaurs are
interesting because they're

the first group of vertebrates
to evolve powered flight,

long before birds
and long before bats.

NARRATOR: The hunt has
brought him to Romania,

to the region of Transylvania,

better known as the home of that
legendary monster: Dracula.

GARETH: 70 million years ago
the climate in this area

was much different.

Big islands in a tropical
sea with lush vegetation,

lots of animal and plant life,
and quite high temperatures.

It couldn't be more different
to the weather today.

NARRATOR: These red
sandstone cliffs hold a
huge number of fossils.

As the rock erodes, more
and more are revealed.

GARETH: So what we have here
are some of the bones of

pterosaurs that we've
collected from this area in

the last few years.

This one, for example, it's
about six centimeters in length,

so it would have come from
an animal that would have

had a wingspan of one
or two meters, six feet.

Average size for pterosaurs.

NARRATOR: But then, in 2008,
Gareth's colleagues climbed

down the cliffs and discovered
something extraordinary.

GARETH (off-screen):
This neck vertebra from
the same part of the neck

in a giant pterosaur.

It's quite short,
quite robust,

but gigantic compared to
a normal sized pterosaur

vertebra that
you can see here,

and you can see immediately
that we're looking at animals

of gigantic proportions.

NARRATOR: When the neck bone
was mapped onto a model of the

pterosaur skeleton, it became
clear that this was one of the

largest members of
the pterosaur family
ever discovered,

comparable to giant
specimens found in the USA.

At up to 16 feet tall,
these massive pterosaurs
could stand nearly

three times taller
than a human,

tall enough to look
a giraffe in the eye.

Their front limbs were
also vast wings that,

when unfurled, could stretch
up to 36 feet across,

the same as a modern Lear jet.

It had a beak more
than five feet long,

perfectly suited to
preying off other animals,

and no living creature has
ever had a larger wingspan.

While it seems obvious
that giant pterosaurs flew,

they're so large experts
have puzzled over how they

ever got off the ground.

We already know
that pelagornis,

with its 24 feet wingspan,

was as big as a bird
could get and still fly,

the difficulty of just getting
off the ground at this size

stopped flying
birds getting any bigger.

So how did a 550
pound pterosaur,

with a 36 feet wingspan,
get into the air?

Flight biomechanics
expert, Mike Habib,

has made it his
mission to find out.

He has been studying the
bones of one particular giant

pterosaur, Quetzalcoatlus.

Discovered in Texas, this
species is of similar giant

size to the one found
in Transylvania.

Mike focused his attention
on the pterosaur's wing.

MIKE: This is the skeleton
of Quetzalcoatlus.

You can see the massive
bones of the wing.

This is called the humerus;

it's the bone of the upper arm.

NARRATOR: Mike conducted a
forensic analysis of the bones.

MIKE (off-screen):
I used CT scans to
look inside of the bones,

and I found that most
of the bones of the
wing were very hollow.

The bone wall is only
three millimeters thick.

It's mostly air by volume.

NARRATOR: This makes
the skeleton very light.

But, inside the
upper arm bone,

a dense internal scaffold
reinforces the bone,

especially near the shoulder,
and that's not something you

see in a bird wing.

This bone is far stronger
than needed for flight,

stronger even than
needed for walking.

So why would the pterosaur
possibly need such
powerful forelimbs?

Then Mike noticed
another clue,

a giant groove in the bone.

This could mean only one
thing, a huge tendon.

MIKE (off-screen): A
giant tendon would run in,
along the groove here,

and then wrap around
the wing pivot joint,

and end up at the
tip of the wing.

The tendon would have
been about as big
around as my wrist.

NARRATOR: The supersize of
this tendon led Mike to form

a unique theory.

The pterosaurs were using
the tendon's elastic power

to catapult themselves
into the air.

MIKE: Tendons, and the
muscles attached to them,

have a certain amount
of springiness.

You can stretch them
and then they snap back,

basically a giant crossbow.

NARRATOR: Mike used the
skeleton to model how this

might work.

MIKE: A giant
pterosaur like this one,

to take off would start by
crouching on tis back legs,

then it would unload
the legs first,

vaulting over the giant wing,
and then it would push against

the ground, using up all that
stored energy and pushing

itself as fast as
possible into the air.

NARRATOR: There is still one
living creature that uses this

kind of vaulting launch.

It's plain to see when you
watch a vampire bat take off.

But vampire bats only
weigh two ounces.

So, could the same
principal work on the scale
of a giant pterosaur?

Mike has come to a local
firing range to find out.

MIKE: So what we have here is
a modern crossbow and it's a

very effective way of
talking about pterosaurs.

Giant pterosaurs
would be stretching its
tendons by crouching,

and the crouch phase
would be much slower

than the launch phase.

So it puts the
energy in slowly,

and then lets it out quick.

So I'm going to put in the
energy here nice and slow.

You'll notice that the limbs
on the crossbow are bending.

That's the energy being stored
in the flexing of the limbs.

There's a lot of
energy in here,

and when I let out to fire the
bolt, it's going to go really,

really fast.

NARRATOR: This catapult
crossbow stores so much energy

it can fire a bolt at up
to 218 miles per hour.

MIKE: Wow! It's a lot
of energy in this bow.

It doesn't have much
kick, because it's
really well engineered,

but you can tell that bolt's
coming out of it real fast.

NARRATOR: The crossbow can
fire this lightweight bolt

hundreds of feet
through the air.

MIKE (off-screen):
Not a bad shot.

NARRATOR: But how do these
mechanics scale up to a

550 pound pterosaur?

MIKE: By storing all this
energy in his giant tendon,

big pterosaurs would have
been able to take off like a

rocket, launching a mass about
the same as a grizzly bear

into the air in
under half a second.

NARRATOR: Mike calculate that
pterosaurs only needed to get

six feet off the ground.

That would give them just
enough room to unfurl their

vast wings and beat
for the first time.

Then, when they're airborne,
just like giant birds,

they glide.

These giants were the largest
flying creatures ever,

but they would have been no
match for the next beast on

our list, a snake
of astonishing size.

NARRATOR: This is the story of
a creature that looks like it

belongs in a
Hollywood B movie.

It begins in 2004, in the
Colombian region of Cerrejon.

A vast mining operation had
expose a fossilized forest

dating to just after the
extinction of the dinosaurs.

Paleontologist Jonathan Bloch
led an expedition to the site.

He returned with
something extraordinary.

JONATHAN (off-screen):
This is what we found.

This is a
recognizable vertebra.

When we originally
discovered this,

we thought maybe it was the
vertebra of a crocodile.

NARRATOR: But this
was no crocodile.

John had identified the
vertebra of the largest snake

ever to roam the
earth, titanoboa.

JONATHAN: This is the largest
vertebra from the backbone of

a 17 foot long anaconda,

which is the most massive
snake alive today.

NARRATOR: When you compare
the anaconda vertebra to

the 60 million year-old fossil,

titanoboa's true size
becomes clear.

JONATHAN: That comparison is
really incredibly dramatic.

It even still takes
my breath away.

NARRATOR: Using the
anatomy of today's giant
snakes as a guide,

Bloch's team set about
reconstructing titanoboa's

skeleton, piecing
together the fragments.

They called in fossil
snake expert, Jason Head,

to verify their findings.

JASON: The numbers that
we kept getting were so

incredible in terms
of its weight and its
length and its girth,

at first I was suspicious we
were doing the math right.

NARRATOR: At two and
a half feet across,

titanoboa would struggle to
fit through your front door.

Weighing in at over a ton, it
would be four times heavier

than the largest
snakes alive today.

And, at 45 feet,

it would be as long as
an American school bus.

JASON: So we're looking at
a lower jaw that would have

been, you know, this long,
about four times the size of a

large giant python today.

Titanoboa theoretically could
have probably opened its mouth

wide enough for you or I
to actually stand in it.

JONATHAN: Right.

NARRATOR: What's clear is
that this snake was simply too

large to live on land.

JONATHAN (off-screen): Because
it was such a massive snake,

it would have had trouble
supporting its own weight.

This animal probably would
have had to spend most,

if not all of its
time in the water.

NARRATOR: And it would have
found plenty to prey on.

JASON: In its ecosystem,
titanoboa lived with
giant crocodilians,

lived with giant turtles
and these giant fishes,

and it probably could
have eaten all of them.

NARRATOR: It's some
60 million years since
titanoboa became extinct,

so it's a little
difficult to meet one now.

But, again, experts can use
today's snakes to get close.

This is a reticulated
python, the longest
species alive today.

JASON (off-screen):
These are the closest
living relatives to titanoboa,

and a lot of their anatomy
is similar to titanoboa and,

from that, we infer
very similar behaviors:

constriction,
ambush predation.

In the case of anacondas,
living in aquatic environments.

Oh, (choking).

NARRATOR: At this moment
in our interview,

Goldie the python chooses
to flex her muscles.

JASON: That's better!

NARRATOR: This
isn't an attempt to
treat Jason as prey,

it's simply her
normal movement.

JASON: Is she in
a good mood still?

NARRATOR: But when actually
on the hunt, she'd deadly.

JASON: When boas and pythons
constrict their prey,

they're putting so
much pressure on the
circulatory system

of the prey animal that they
actually induce a heart attack.

They can stop the heart
by squeezing so hard.

NARRATOR: Snakes have been
recorded constricting at

25 pounds per square inch.

Delivered by a snake
titanoboa's size,

that would easily be enough
to crush as big as a rhino.

To find out what this
kind of force looks like,

snake expert Rhys Jones is
overseeing a little test,

using a collection
of heavy machinery.

RHYS: We've got an experiment
set up which will help us to

try and visualize exactly
the type of forces needed to

overcome these
huge prey items.

So what we've got here,
we've got a truck.

This is fixed in place.

This big yellow rope here is
representative of our snake

and it's got, as you see,

two coils here
around this oil drum.

The oil drum is
representing our prey item.

It's full of
water, it's sealed.

That's going to take
some pressure to be
able to crush that,

so we're going
to need muscle.

NARRATOR: Cue a seven
ton tractor with a
190 horsepower engine.

This versus a sealed barrel
ought to be a tough test.

As the tractor pulls on,
the pressure passes 25psi;

that's the pressure of
today's largest snakes.

But titanoboa had four
times the muscle mass,

and estimates say it could
pull off crushing forces of up

to 110 pounds per square inch,
the same pressure as having an

eight ton truck
parked on your chest.

(explosion).

RHYS: Oh look!
It's just squeezed it
like a toy, hasn't it?

That is just incredible.

I think our snake pretty
much nailed it, don't you?

NARRATOR: It only took
55psi to burst the barrel,

half what titanoboa
might have done,

more than enough to crush the
life out of any living thing.

RHYS: I mean look at the
damage to this oil drum.

Can you imagine if
that type of pressure
was applied to you?

You wouldn't last two seconds.

NARRATOR: Titanoboa's
phenomenal crushing force

made it the apex predator on
Earth for ten million years.

(groaning).

Titanoboa was the largest
snake in Earth's history.

Nearly twice the wingspan
of the biggest flying bird,

and nine feet longer
than the wingspan of

the largest flying creature.

But, as massive as
this predator was,

next up is a beast even
bigger and more terrifying.

NARRATOR: At first glance,
this beast looks like a cross

between a giant turtle
and a mega crocodile.

But what this submarine
sized sea monster really was,

and how it became
apex predator,

has become a 100 million
year old mystery.

In 2003, new evidence
came to light

on the south coast of the UK.

If you're looking for fossils,
the Jurassic coast of Dorset

is one of the most fertile
hunting grounds on Earth.

Kevan Sheehan has been coming
here for more than 40 years.

KEVAN (off-screen): I
saw three pieces of what I
thought was fossilized wood.

I got really excited
because I thought wow,

there's got to be more of
this, and then, joy of joys,

there's this huge
piece of bone stuck,

It's almost like a meteorite
has gone bang into the cliff.

NARRATOR: Embedded in
the cliff were dozens
of pieces of fossil.

Reassembled, they made
something incredible.

The most complete skull ever
discovered of a pliosaurus.

Paleontologist,
Richard Forrest,

is an expert on these
ancient monsters.

RICHARD: This is a
giant killing machine.

This pliosaur was
the top predator,

it was the peak
of the pyramid.

They were basically just
big, powerful brutes that

devastated anything
in their way.

It's an awesome animal.

NARRATOR: The biggest known
pliosaurus had flippers

nine feet long.

That's like a basketball
player at full stretch.

If it swam in today's waters
it would have been bigger than

a Navy patrol boat,
that's 45 feet.

In terms of weight,

it would have taken
about 44 compact cars

to balance out one pliosaurus.

The strongest biter alive today
is the saltwater crocodile,

with a bite force of 1.8 tons.

Pliosaurus had a bite
nearly ten times stronger.

It was the T-Rex of the ocean.

RICHARD (off-screen): We have
these great teeth at the front,

which is where it grabs the
prey; that's what catches it.

Then it moves a
bit further back,

then another set of teeth,

and these are the ones that
cut the prey up into pieces.

Then we have these teeth,
which are hooked backwards,

so once the prey gets to
there, there's no way out.

NARRATOR: But that
throws up questions.

If you're going
to bite something,

you've got to be able
to catch it first.

So how does a 45 feet
predator the size of a

large shipping container
keep up with its prey?

The secret must lie in their
four boat-size flippers.

The closest match to a
pliosaurus flipper today

belongs to a creature
altogether less frightening.

Penguins may look funny
when they waddle on land,

but underwater
they're like rockets,

whizzing around at speeds
of up to 20 miles per hour.

Biomechanics expert,
Flavio Noca, is trying to

understand how they reach
these extraordinary speeds.

Using a high speed camera,

he films penguins moving
around underwater.

FLAVIO: This camera is
actually able to go up to

12,000 images per second.

NARRATOR: That means that
every minute detail of flipper

action is captured.

Flavio's footage reveals that
penguins aren't swimming with

their flippers, they are
flapping them like a bird.

They're flying underwater.

And, by twisting their
wings as they flap,

penguins can propel themselves
forward on the upstroke as

well as on the down stroke,
which is something most

airborne birds can't do.

The pliosaurus had, not
two, but four flippers,

and they were gigantic.

All signs point to this
mega monster being not
only one of the biggest,

but also one of the fastest
predators in the ocean.

Aerospace engineer,
Luke Muscutt,

is investigating
how they moved.

Using X-rays of fossils,
Luke has recreated a pair of

pliosaur flippers
he calls wings.

LUKE: Pliosaurs were
really good swimmers,

and the aim of the game is
to chase down the prey and,

obviously, to do that
you need to be very fast.

You need to have a high thrust
and a high acceleration.

NARRATOR: By suspending
the wings in a tank,

he's trying to determine how
the front and back wings work

together to propel
the pliosaurus.

Blue and red dyes reveal how
each wing moves the water.

Luke moves the wings
together in different ways,

and records the amount
of propulsion generated.

He notices certain movements
have a remarkable effect on

the back wing.

LUKE (off-screen): So,
initial results suggest
that the hind wing can

produce a thrust which is
about 50% higher than

a wing operating on its own.

NARRATOR: By harnessing
the wake of the front wing,

the pliosaurus could generate
two and a half time as much

thrust as it would with
just one set of wings.

And that is how this mega
beast gained sudden and

tremendous acceleration.

Its prey wouldn't
have stood a chance.

Pliosaurus is just the latest
on our lineup of the

Top Ten Biggest Beasts Ever.

So far, we've
revealed, griffinfly,

the biggest insect
in Earth's history.

Pelagornis, the
largest flying bird.

Paraceratherium, the greatest
mammal to walk the earth.

Giant pterosaurs, the largest
flying creatures ever.

Titanoboa, the largest
known snake of all time.

And pliosaurus, the largest
predatory marine reptile.

But coming up is a bizarre
dinosaur that beats them all.

NARRATOR: New discoveries of
one of the strangest dinosaurs

ever are rewriting
the textbooks.

A monster dinosaur
with vicious teeth,

claws almost as
big as a human arm.

PAUL: We're talking something
of enormous length that could

slice you with one motion.

NARRATOR: And a
massive spiny sail.

NIZAR: The spines are
taller than a person.

Every now and then
we come across really
bizarre dinosaurs.

In my book it's the most
bizarre dinosaur out there.

NARRATOR: Paleontologist,
Nizar Ibrahim, was on

expedition to the Sahara
Desert in Morocco in 2013.

When he saw the beast's bones,

he knew he had
something special.

This was a Spinosaurus,
or spine lizard.

It lived 100
million years ago.

Everything about
Spinosaurus is vast.

NIZAR: Seeing it in front
of you, you realize wow,

this is one big predator.

NARRATOR: That seven feet
spiny sail means Spinosaurus

stands twice as
tall as a human.

At 50 feet long
from snout to tail,

it is ten feet
longer then T-Rex.

it's so big it's the
size of a fire truck,

weighting in at 22 tons, this
is the biggest predator to

ever walk the earth.

But Spinosaurus wasn't the only
dangerous dino on the block.

100 million years ago,

this desert was a
vast river system,

bursting with other
giant predators.

NIZAR: I call the it
the River of Giants,

because it was home to giant
fish, giant flying reptiles,

several T-Rex size
predatory dinosaurs.

It was probably the most
dangerous place in the

history of our planet.

PAUL: It's jam-packed with all
these predators to the point

where you say what
were they living on?

Where were the herbivores to
support this many predators?

NARRATOR: It was a mystery.

With so few plant-eating
dinosaurs to feed on,

what enabled Spinosaurus to
survive here and become the

biggest predator of all?

As Nizar and his team
looked closer at the bones,

they began to find clues.

Strange features that mark
this predator out from other

dinosaurs, like T-Rex.

NIZAR (off-screen):
This animal didn't look
anything like T-Rex or other

predatory dinosaurs.

It was like working on an
alien from outer space.

NARRATOR: For starters, the
teeth were an unusual shape.

NIZAR (off-screen):
Spinosaurus is really all
about grabbing prey and

holding it in these massive
jaws with long, conical teeth.

So these teeth are great
to grab slippery prey.

NARRATOR: At over five
feet long, these jaws

were capable of swallowing prey
the size of a person, whole.

Next, Nizar noticed that,
for a predatory dinosaur,

the front limbs
were unusually long.

Though not all experts agree,
Nizar believes Spinosaurus

may have even
walked on them,

and the back feet
were just as strange.

NIZAR: Now the
feet of Spinosaurus
are really bizarre.

Typically in predatory
dinosaurs the claws would

be recurved to grab prey
and pin it to the ground.

In Spinosaurus, the
claws are almost flat,

and they're quite wide.

It almost looks like a paddle,
and I think it's quite likely

that the feet of
Spinosaurus were webbed,

just like in many
birds or crocodiles.

PAUL: This has more to do
with paddling and swimming

than running on land.

NARRATOR: Everything was
pointing in one direction.

This looked like a beast that
swam and hunted in water.

PAUL: This was a dinosaur
that was doing something

no other predatory
dinosaur was adapted to do.

NIZAR: This is
a river monster.

NARRATOR: This was an
extraordinary discovery.

It suggested Spinosaurus
hunted fish, giving it

a major advantage over the
other dinosaurs predators.

But if Spinosaurus was
swimming, how did it hunt?

How could something this
bulky chase down enough

fast moving fish to
grow to monster size?

To find out, the team
scanned the bones.

A CT scanner allowed
scientists to record the

fossils in 3D and
see inside them.

Suddenly the skull from
another Spinosaurus started

to reveal new secrets.

NIZAR: This is the tip of
the snout of Spinosaurus.

So, when you look at the
outside of the snout,

you have all these openings
and it's really unusual.

NARRATOR: The CT scan revealed
that, inside the skull,

a complex network of
tubes runs from the
holes to the brain.

NIZAR: it's really a
network of openings,

and so clearly there's
something happening there.

There's probably some
kind of sensory function.

NARRATOR: It reminded Nizar
of some of today's deadliest

predators, crocodilians.

Crocs and alligators have
similar holes on their snouts.

They're called foramina,
and, for many years,

they too mystified experts.

Neurobiologist, Daphne Soares,
made it her mission to find

out what they were for.

DAPHNE: Wow! As you can see,
these animals are really well

adapted to living in the water.

NARRATOR: Daphne devised
an unusual experiment.

She put young
alligators into a tank,

blocked up the foramina
on their snouts and then

turned out the lights.

DAPHNE: I have the animals
in complete darkness so they

can't see, and their ears are
covered so they can't hear.

NARRATOR: Then, to mimic the
movement of small prey falling

in the water, Daphne hit
upon using water droplets.

DAPHNE: And I'm using water
droplets because they don't

smell like anything.

NARRATOR: With all their
senses neutralized,

the alligators
didn't react at all.

Then Daphne unblocked
just the snout holes

and repeated the drip test.

Daphne's experiment revealed
that the openings in the

‘gator's snout hid pressure
sensors that can pick up the

tiniest motions in water.

This super sense gives crocs
an astonishing reaction speed

of five-hundredths of a second,

as fast as a
Lamborghini gear shift.

The holes in Spinosaurus's
skull likely hid similar

pressure sensors.

PAUL: This is the super sense
that allowed Spinosaurus to

become the ultimate predator.

NIZAR: You can just imagine
Spinosaurus plunging its huge

jaws in the water and
detecting movement and

then catching prey.

NARRATOR: This super sense,
and the ability to hunt in

water as well on land made
Spinosaurus the biggest

predator to ever
walk the Earth.

But coming up the next giant
beast is the biggest apex

predator of all time.

NARRATOR: Stalking the
oceans from 16 million to
three million years ago,

the biggest apex
predator ever: megalodon.

The name simply
means big tooth,

and it seems to have been the
most voracious shark ever.

STEPHEN: There was nothing
that was safe from megalodon.

If it could catch
it, it could kill it.

NARRATOR: Much about this
giant remains mysterious,

but new clues are coming
to light in Panama,

Central America in, of all
places, a cement quarry.

Here, giant excavators are
digging through the bed of

an ancient coastline.

CATALINA: Ten
million years ago,

this area was
covered by water.

We know that because of the
kinds of fossils we find here.

For example, we find plenty
of these shells that are

typical from shallow
watered areas.

NARRATOR: But, as well as
shells, paleobiologist,

Catalina Pimiento, is also
finding megalodon teeth,

and there's something
strange about them.

CATALINA: The teeth that we
find here from megalodon are

very small, relative to
a typical megalodon teeth

that we find in other places.

I know these are megalodon
teeth because they are a
particular shape.

They are triangular and
quite symmetrical but,

most importantly,
because of the serrations
they have on their edges.

NARRATOR: There's only
one logical conclusion.

CATALINA: The reason
is that most of them
were babies or juveniles.

NARRATOR: Catalina has made
an astonishing discovery,

the first ever evidence for
a megalodon breeding ground.

CATALINA: This area
right here is the first
nursery area for megalodon.

NARRATOR: But even amongst
these infant specimens,

megalodons extraordinary
size was striking.

The baby's teeth were
as big as those of
today's deadly giants,

the adult great white.

CATALINA: This is
megalodon baby tooth,

and this is an adult
great white shark.

You can see here that the
baby megalodon was as big

as an adult great white.

So imagine when they born,
megalodon babies were huge.

NARRATOR: The fact that
Catalina had to make her

deductions using teeth
alone isn't unusual.

In fact, almost everything
that experts know about

megalodon comes from
looking at its teeth.

STEPHEN (off-screen): We don't
find the skeletons of megalodon

because, just like
living sharks,

they're made of cartilage
and after the shark dies the

cartilage disintegrates.

But we do find their teeth,
and we can use these teeth to

recreate what the jaws
would have looked like when

megalodon was alive.

NARRATOR: What they
tell us is that the adult
megalodon was a Goliath.

Its jaws alone were
up to seven feet high,

easily tall enough
to swallow a person.

Weighing in at a
whopping 100 tons,

it was 100 times heavier
than an average Great White.

And, at 60 feet long,

it was the length of
an articulated truck.

And that jaw,

up to 250 teeth lined the
mouth in several rows,

with edges serrate
like a steak knife.

STEPHEN (off-screen):
I mean these teeth
are just so powerful.

The massive jaw muscles
that this animal had to
close these jaws,

it would just dismember
any animal that was alive

on earth at that time.

NARRATOR: And Stephen has
evidence of just what these

jaws could do to prey.

STEPHEN: We know from the size
and shape of this bone that it

is a dolphin tail vertebra.

It's right down
near the fluke.

There are these deep
gouges on either side.

The only way that this fossil
could have these deep gouges

was that it was bitten
forcefully by a megalodon.

So if we look at
a megalodon tooth,

so the upper jaw slams shut,
forcing the vertebra down into

the wedge between
two adjacent teeth,

deeply gouging the bone with
such force that it probably

severed the tail off.

NARRATOR: Everything
points to an astonishingly
powerful bite,

and one man who has set
out to calculate exactly

how strong that bite is, is
shark biomechanics expert,

Dan Huber.

Dan starts with a CT
scan of the skull of
a modern Great White.

HUBER: After the white
shark's head is CT scanned

we can create a
computer model of it.

We can see the lower
and the upper jaws here,

and then we can apply virtual
muscles to those virtual jaws

and run simulations to figure
out how hard it can bite.

NARRATOR: Next, Dan scales
up to megalodon size.

HUBER: And if we apply these
numbers to what we think is

the biggest megalodon
that's ever existed,

its posterior bite force
was about 41,000 pounds,

or about 18,500 kilograms.

NARRATOR: That's like the
weight of a garbage truck

pressing down on
the back teeth.

So what does a bite force of
this size look like in action?

To find out, Dan is
going on a mission.

He's joining up with
the Tampa Fire Brigade,

and a piece of kit they
use for cutting victims
out of crashed cars.

The jaws of life.

DENNIS: It's lightweight,
it's really easily deployable.

HUBER: So is this thing going
to be able to generate

41,000 pounds of bite
force, the corner of it?

DENNIS: Absolutely, Dan.

That's exactly where
it's going to cut.

So this shouldn't have any
trouble at all when we need

to cut open cars.

HUBER: So that's actually
pretty similar to what we're

looking at with this
ancient shark, megalodon.

Alright, let's see
what this thing can do.

DENNIS: Alright, let's do it.

NARRATOR: First, Dan tries
out the jaws on a cow bone.

Something similar to what
megalodon got to chew on.

DENNIS: Just go head.

HUBER: See, it split the thing
in half, no problem at all.

NARRATOR: Next up is the car.

The jaws of life can deliver
the same kind of bite force

as megalodon only
far more slowly.

Megalodon was capable of
biting through the car

in a split second.

HUBER: From this, we know
that megalodon can tear
through ancient whales,

we know that it could tear
through ancient sea turtles

and apparently it could
even tear through this car.

Megalodon was the biggest
predator that's ever existed,

and its bite force was the
highest bite force that's ever

happened in any animal in
the history of the planet.

NARRATOR: Megalodon tops
all other apex predators.

It was nearly one and a half
times the length of titanoboa.

It was more than twice
the mass of pliosaurus,

and it would have
dwarfed Spinosaurus.

But though this giant
shark was the biggest
apex predator ever,

it shared the ocean with
something much, much bigger.

NARRATOR: They are the largest
living creatures on earth,

and the heaviest in history.

Propelled by vast tails,

they spend much of their
time in the deep oceans.

But every year
come summertime,

blue whales appear in the
waters just off Los Angeles.

For ecologist,
Ari Friedlaender,

it's an unmissable
opportunity to study them.

ARI: You get close up
to them and you start
to see how big they are.

You start remembering
what it feels like to be
this tiny little person

in a pretty small boat next
to this enormous whale.

It's kind of
daunting, you know?

They're, they're huge.

NARRATOR: The numbers
are awe-inspiring.

The whales are so big
compared to a person that

90 of us could fit
on its tail alone.

Its 200 ton bulk

makes it 30 times heavier
than an African elephant and,

at 100 feet, it's the
same length as a Boeing 737.

So how does a
mammal get so big?

It's only when a whale washes
up dead on the beach that

scientists get a chance to
really study their anatomy.

DON (off-screen): Now we're in
the rib cage of the whale,

and either side of the rib
cage would be the lungs.

You've got the heart,
you've got the stomach.

NARRATOR: A heart the size of
a car connects to a million
miles of blood vessels,

enough to reach to the
Moon and back twice.

But there's one feature that's
supersized beyond all others:

the mouth.

Rather than hunting
one big animal,

blue whales use their
enormous mouths to catch

entire shoals in one go.

They feed on tiny shrimp-like
crustaceans called krill.

DON: Many people think that
it's amazing that the largest

animal that's ever existed
feed on such a tiny animal,

but no blue whales are
going, oh, there's a krill,

I think I'll take that one.

What they're doing is
they're trying to find huge,

dense swarms of krill and a
prey item for a blue whale is

not one of these guys, it's
thousands and thousands and

tens of thousands
of these guys.

NARRATOR: Though the whales
is so gullet is small it would

choke on a loaf of bread,

its mouth can take in 220
tons of water in one go.

For anything
roughly comparable,

you'd have to look at
something like this, the DC10.

A specially modified
fire-fighting airliner,

it swapped passenger seats
for a massive water tank.

RICK: This is the biggest
tanker flying in the world.

It carries 12,000 gallons
or 44,000 liters of liquid,

which is roughly four
to ten times the size
of any other airplane.

NARRATOR: Used to
fight forest fires,

the DC10 releases enough
water to cover the length

of ten football pitches
in a single drop.

But a blue whale picks up
four times this much water

in a single mouthful.

RICK: We're very
proud of this machine,

but if the whale could
fly, we'd hire the whale,

'cause it's four times bigger!

NARRATOR: The whale more than
doubles its weight with each

mouthful and what follows is
one of the weirdest operations

in the natural world.

When the whale opens
its mouth to feed

the water pushes its elephant
sized tongue all the way back

to its belly button.

The tongue is super
stretchy and expands out,

lining the mouth and
creating a huge sac
full of water and krill.

Then, mouth closed,

the whale rams the tongue
forward like a piston.

It forces the water out
through sieve-like grilles

called baleens until only
the krill is left inside.

The energy required to perform
this maneuver is colossal.

In fact, in a single day,
blue whales burn up to
three million calories,

the equivalent of
10,000 hamburgers.

How does a creature burning
this much energy find enough

food to become a giant?

The answer must lie
in how they hunt.

But, as whales hunt krill
hundreds of meters underwater,

witnessing this
behavior has been almost
impossible until now.

Ari Friedlaender is using a
tag that enables him to spy on

whales even when they're
deep below the surface.

It contains a camera and
motion detectors like the ones

found in a smart phone.

All he needs to do now is
attach it to a 200 ton whale.

ARI (off-screen):
You always are a little
nervous approaching them.

They're wild animals,

so you never know how
they're going to react.

NARRATOR: Ari gets
into position.

Tag in place, the whale
disappears into the depths

and Ari returns to base to
track it on his computer.

As he plots the
whale's position in 3D,

he spots something
extraordinary.

ARI: incredibly exciting.

Up until now, we basically
thought they just went through

the water, taking these
munches, and lunging,

sort of in a straight line,
but we noticed the animal's

diving down to depth and then
is doing these 360 degree

rolls, and this kind of
acrobatic maneuvering is

something we had no idea an
animal this big could do.

NARRATOR: Images from the
camera reveal the whale rolls

just before it opens
its mouth to feed.

ARI (off-screen): This is
the mechanism that allows
whales to get so big.

If you're a whale, your eyes
are on the side of your head.

They don't have this
binocular vision like we have,

where you can see
directly forward.

So, in order for that animal
to see its prey in front it,

it kind of needs to roll
its body to maximize the

amount of food you get
and you limit the amount of

energy it takes to do it.

NARRATOR: Far from just
hoovering up krill like a

200 ton deep sea juggernaut,

it turns out the blue whale
is the ocean's biggest acrobat.

So far on Top Ten Biggest
Beasts Ever, we've met,

the hawk-sized griffinfly,

a bird the size of
a fighter plane,

a mammal
as big as a tank,

a pterosaur the
size of a Lear jet,

a snake the length
of a school bus,

an ocean killer
nearly 50 feet long,

a dinosaur that dwarfs T-Rex,

a shark 100 times heavier
than a Great White,

and the largest creature
ever to swim Earth's oceans.

The blue whale is very
nearly the largest beast
that's ever lived,

but there's one beast
that's even longer and it

takes the title of
biggest beast ever.

NARRATOR: March, 2015.

In southern Argentina in the
remote province of Patagonia,

a team of paleontologists
is on standby.

(truck horn).

Lucio Ibiricu has been waiting
for this moment for months.

(speaking Spanish).

NARRATOR: Inside this truck
are some of the biggest
bones on the planet.

LUCIO: It's really
good, I'm really happy.

Everything here now.

NARRATOR: And after five
years in the United States

undergoing scientific
analysis, they're coming home.

More than 50 crates hold the
bones of just one dinosaur.

Each bone is enormous.

Yet, as big as they are, these
bones are just a clue to a

creature that was even larger,

the biggest beast ever
to walk the Earth.

The journey to this
moment began in 2005.

Lucio was part of a team of
paleontologists prospecting

for dinosaur bones.

They were in a remote
area of Patagonia known
as the Bad Lands.

LUCIO: 75 million years ago

this area was
completely different.

Warmer,

more green,

humid,

a lot of vegetation,

and several rivers.

NARRATOR: The ancient rocks
reveal the area was once a

perfect habitat for dinosaurs.

But today the lush
forests have given
way to harsh desert.

As the team surveyed the land,
one of them came upon a small

piece of exposed bone.

LUCIO: The first
thing that we see was

the middle part of the femur.

So we started to dig,

and continued digging,

and we never finished with that.

So we say, 'ok this is
the femur but it's huge'.

KENNETH: You sit there and you
look at this object and you

realize that you're the first
person to ever see this thing,

you're the first person in
history to know about this.

NARRATOR: They had found
a giant thigh bone,

over six feet long.

LUCIO: So, this is the femur.

This is a leg bone.

It's bigger than me -
and it's just one bone.

This is amazing.

NARRATOR: It's
hard to imagine,

but bones of a beast bigger
than this have occasionally

been discovered but what was
remarkable about this find was

just how complete
the skeleton was.

It took several expeditions
to uncover it all.

KENNETH: At the end of
three seasons of excavating
there we had 145 bones.

NARRATOR: And the state
of them was surprising.

LUCIO: The preservation of
the dinosaur was very good.

A lot of the bones that we
found are in the same position

as when the dinosaur died.

NARRATOR: The team were
now in possession of
what was, effectively,

a time capsule, one
that could revolutionize
our understanding

of the biggest beasts
to ever roam the Earth.

Ken took the bones back to
his lab in Philadelphia.

Here, careful cleaning,
3D scanning and forensic

examination all started to
reveal how these extraordinary

beasts looked and lived.

The beast's sheer size was
apparent at every turn.

KENNETH (off-screen): The scale
just staggers the imagination.

This animal was 85 feet
long from head to tail.

It was two and a half
stories tall at the shoulder.

NARRATOR: This was a new
species of titanosaur,

a plant-eating dinosaur
of almost unimaginable
proportions.

Ken named his titanosaur
Dreadnoughtus,

meaning ‘fears nothing'.

KENNETH (off-screen):
Dreadnoughtus isn't going
to have anything to

worry about in
terms of predation.

These are big, nasty, capable,
vigorous creatures that

deserve a lot of respect.

NARRATOR: Dreadnoughtus
was clearly a mine of

information for the scientists.

But it held one surprise
which relates directly to

the size of the very
biggest titanosaurs.

Cutting into the bones,
Ken started to find
evidence of how old

this Dreadnoughtus
was when it died.

KENNETH: Can you see
here these big oval
bone cells, here?

That's indicative of bone
that's not growing any more.

And then, as we move towards
the outer edge of the bone,

you'll notice that that
texture changes and that is

indicative of
rapidly growing bone.

NARRATOR: And that could
mean only one thing,

Ken's Dreadnoughtus, though
vast, was not fully grown.

KENNETH: We know that it was
growing rapidly when it died.

So, 65 tons and not
yet done growing.

That means there are bigger
Dreadnoughtus out there;

we don't know how big this
dinosaur could have gotten.

NARRATOR: But then
comes another clue,

titanosaur wasn't
like our other giants,

Megalodon and Blue Whale,

it didn't start life
at monster size.

Paleontologist,
Gerald Grellet-Tinner,

has uncovered stunning
evidence that reveals the

last piece of the jigsaw.

He's investigating a site
in northern Argentina..

an area that was once a
harsh, volcanic landscape.

GERALD: So here we're sitting on
top of a geothermal formation.

NARRATOR: At the time
of the dinosaurs,

this area was a
geothermal hotspot,

with steaming vents
and hot water pools.

Gerald has found evidence
that titanosaurs came here
to lay their eggs.

GERALD: What we
have here is a clutch

of about 24, 25 Titanosaur eggs.

And this one here, it's
probably the biggest one

and I would say maybe more than
eight inches in diameter.

NARRATOR: Remarkably, as
big as titanosaurs were,

their eggs were about the
same size as ostrich eggs,

but some of them have
incredibly thick shells.

GERALD: As you can see,
this one, for instance,
it's very, very thick.

It's about 7mm

and this is virtually
impossible to break.

So a chick would not be
able to break that eggshell.

NARRATOR: Gerald thinks that
the shells began this thick to

shield the embryo inside from
the geothermal chemicals,

but then these chemicals
helped make it possible for

the baby titanosaur to hatch.

GERALD: The harsh chemical
is eroding the eggshell

from the outside to the inside,

thinning down the eggshell
to probably 1.2-1.3mm,

which is perfectly acceptable

for the chick to break.

NARRATOR: And, for
an incubating egg,

the choice of this site
offered a major plus,

it had constant heat.

But baby titanosaurs
had one big problem,

once hatched they were no
bigger than domestic cats,

not great in a world teeming
with hungry predators.

KENNETH: There was a
premium on growth when
you're on the menu,

and so they grow very
rapidly to get to the point

where they can be
impervious to predation.

NARRATOR: And going from the
size of a cat to having thigh

bones over six feet long means
one serious rate of growth.

KENNETH (off-screen):
Baby titanosaurs have an
early burst of growth and

that burst never stops.

They just keep growing as
fast as they possibly can.

NARRATOR: It should now
be possible to pull all
the clues together

and build a picture of what
these beasts looked like.

Starting with
scans of the bones,

Ken Lacovara works
on a 3D digital model
of Dreadnoughtus.

The completeness of the
skeleton means this model is

far more accurate than for
any previous titanosaur.

And this gives us an
amazing opportunity.

We can take the model and
scale it up to match the bones

of Argentinasaurus, the
largest titanosaur ever found.

Only a handful of
Argentinasaurus's bones

have ever been discovered,

so this may be our
best possible chance

to fill in the blanks
and see what the beast
might have looked like.

Just how big that is must
be seen to be believed.

LUCIO: So, one of the...

...of the best ways...

...to have an idea...

...how big this
dinosaur could grow

is to measure it.

So we are going to
start with the tail.

NARRATOR: Using
Dreadnoughtus's
skeleton as a guide,

Lucio maps out how
Argentinasaurus may have
stood on this ground.

Its tail alone would
be the length of
titanoboa at 45 feet.

LUCIO: So this is the tail.

NARRATOR: Adding its body
takes Lucio to 70 feet,

longer than megalodon.

LUCIO: So this is
the tail and the body

and now the neck.

NARRATOR: The neck and
head is another 60 feet,

giving a total
length of 130 feet.

That's bigger
than Blue Whale and
paraceratherium put together.

All the pieces in place,
it's time to reveal the

biggest beast ever
to walk the earth.

NARRATOR: Meet
Argentinasauraus,

the biggest beast ever.

LUCIO: From the tail to
the front of the head

should be about 130ft.

NARRATOR: Towering over
30 feet in the air without
even lifting its head,

and with a neck like
the arm of a crane,

the biggest known
titanosaurs would have
been a fearsome sight.

Standing over
three stories tall,

a six feet person wouldn't
even reach the knee of an
Argentinasaurus.

At 90 tons, it likely weighed
as much as 11 T-Rexes.

And 130 feet from
tail to mouth,

it was the length of the
space shuttle orbiter.

Titanosaurs were mega
versions of long necked,

long tailed psauropods
like diplodocus.

Just their stomachs
alone were likely the
mass of an elephant,

and just one foot was big
enough to crush 20 people.

So what was the secret
to their mega size?

Well, an answer appears
to lie with the one thing

about titanosaur that
isn't gargantuan.

Its head.

A titanosaur like
Dreadnoughtus only had a head

as big as that of a horse, and
that's because it didn't chew

its food, it just
grabbed and swallowed.

KENNETH: The skull is
basically a plant vacuum.

They don't have the
ability to chew.

NARRATOR: What that means
is that a titanosaur had the

capacity to consume over two
tons of vegetation every day.

That's enough salad
to feed 40,000 people.

KENNETH: Dreadnoughtus could
stand in one place with its

massive body and
not move that body,

and maybe spend an
hour taking in tens of
thousands of calories,

and then at the end of that,

take a few steps to the right
and spend another hour or so

clearing out another giant
envelope of vegetation.

So, by expending very
few calories itself,

it takes in massive
quantities of food.

NARRATOR: This basic strategy
made titanosaurs some of the

most efficient
eaters of all time,

and it allowed them
to reach monster size.

And yet, as big as they were,
experts are convinced that

somewhere out there,
hidden in the rocks,

are even bigger specimens
still to be uncovered.

The Top Ten Biggest Beasts
Ever are giant creatures

at the top of their
evolutionary trees,

beasts that hunt, kill,

walk, swim and fly at sizes
that dwarf all others.

Between them, they've
mystified scientists,

broken the record books

and colonized every
continent on the planet.

Captioned by Cotter
Captioning Services.