[Birds and insects chirping] ♪ Male Narrator: Over 66 million years ago... [Shriek] [Deep, guttural growl] our world was ruled... [Dinosaur growls] by dinosaurs.

[Dinosaur hisses] [Deep growl] The largest animals that have ever walked the earth.

[Deep growling] Today, dinosaur experts across the globe are uncovering the bones they left behind.

Allowing us to imagine how these extraordinary creatures may have lived.

So that we can tell their stories... [Dinosaur shrieks] and they... [Squealing] can walk again.

[Ferocious growl] ♪ Amongst the jagged mountain peaks... majestic valleys... ♪ and scattered hill towns of central Portugal, an astonishing discovery has been made.

♪ A find so remarkable, it's drawn a team of dinosaur hunters from across Europe.

♪ Buried here are the remains of a colossus.

Francisco: We have a lot of bones in this area.

Pedro: Just amazing.

Narrator: A monumental, long-necked Lusotitan.

♪ This animal is a giant of the Jurassic.

Narrator: Known as Old Grande, he's one of the largest dinosaurs ever to have lived.

♪ And using his bones, we can begin to imagine this giant's story.

♪ In the late Jurassic, our planet looks very different.

♪ Amongst its shifting continents, a small land mass known as the Iberian Meseta, that one day will include Portugal, lies surrounded by ocean.

An island cut off from the rest of the world.

[Birds chirping] Dense, coniferous forest covers much of the land.

♪ [Waves crashing] [Dinosaur squawking] Giving way to windswept beaches on the coast.

[Dinosaur chittering] [Crunching] Here, if you're in luck... [Dinosaur gulps] an easy lunch can be found.

♪ For Torvosaurus, the island's top predator, it's an opportunity worth fighting for.

[Torvosaurus growls] [Soft rumbling] But even these 4-ton carnivores... are no match for the enormous Lusotitan--Old Grande.

[Deep growling] At a staggering 40 tons... he is the undisputed king of the island.

But as a herbivore, he isn't on the hunt for food.

He's been drawn to the beach by the allure... of a female.

[Guttural whimpers] As an aging male, this may be his last chance to mate.

[Distant bellowing] ♪ But female Lusotitans are only receptive for a few weeks of the year... so he doesn't have long to make an impression.

[Grumbling] ♪ 150 million years later... the true scale of Old Grande is emerging from deep beneath the ground.

♪ We definitely have a huge specimen.

All the bones of this animal seems to be more or less complete here.

Narrator: Uncovering the most complete Lusotitan ever discovered is an exciting prospect for paleontologists Francisco Ortega, Elisabete Malafaia, and Pedro Mocho, who have spent years studying these huge creatures.

So I think we have for this animal probably a leg between 3 and 3 1/2 meters.

Narrator: Today, they're starting with how tall Old Grande was, which they can estimate using the bones from his 10-feet-long front limb.

So calculating how tall he is, I would say around 10 meters.

-10 meters.

OK. OK. -Yes, yes, yes.

10 meters tall -is a very big animal.

-It's a big animal.

Francisco: This animal is the biggest animal in this ecosystem.

Pedro: At least the tallest one.

Narrator: At 33 feet high, Old Grande is one of the tallest of his species ever found.

♪ [Birds chirping] Which is certainly one way to impress a mate.

♪ [Grumbling] Female Lusotitans may have been most attracted to the biggest males.

[Snorting] A sign their offspring will be healthy and strong.

So it should be easy for Old Grande to make his mark.

[Crunch] But it's not all about him.

Before they will mate, female Lusotitans must first wait for the seasonal rains... [Branch snaps] making sure there is enough fresh vegetation for their young.

[Crunch] And this year, the rains are late.

[Dinosaur screeches] Old Grande has no choice but to wait.

He must guard her closely and hope there is no other suitor close by.

But love rarely runs smoothly.

3 miles from where Old Grande was found, the team has made an important discovery.

Man: Can you look at this?

-What?

-What do you think?

-What is this?

Elisabete: We need to clean this area more but the bone is here and continues there.

This is bone also.

Francisco: OK.

So this section seems to be a rib.

-A rib fragment.

-This one?

Narrator: The fossilized rib is a similar size to Old Grande's.

But given its distance from the main dig, it's unlikely to be his.

Francisco: It's interesting because this bone is so big.

Has to be another Lusotitan.

Elisabete: It is interesting that we have here, so close, two individuals of this species.

Narrator: Unearthing two Lusotitans so close together is unheard of.

So the team is keen to learn more.

Pedro: Can you put this in place, please?

Narrator: They cover the sections of rib in a layer of plaster... Man: Eh, Alvaro, limpia el tar, por favor.

Narrator: so they can be removed safely... and examined in one piece... which is a massive 10 feet long.

Pedro: You know, this is a huge rib.

Two Lusotitans with such a huge size is definitely impressive.

This is very speculative, but this could be another male.

Francisco: Amazing.

Narrator: Like elephants and rhinos today, Lusotitan bulls were likely solitary and very territorial.

If these two big, strong animals live in the same ecosystem in the same time, there is going to be some kind of competition.

Narrator: Just like Old Grande, this rival male would have been searching for a mate, creating the potential... [Heavy stomp] for a dangerous confrontation.

[Deep growling] Although this contender may be younger than Old Grande... he's not afraid to challenge him for the attentions of the female.

[Deep growling] ♪ [Growls] Old Grande is a seasoned fighter... [Growls] and the largest bull on the island.

A stern warning... [Ground shakes] should be enough to make this upstart back off.

But all is fair in love and war.

[Ground shakes] [Guttural moaning] [Deep growl] The surprise attack leaves Old Grande seriously hurt.

[Guttural moaning] His leg badly injured.

[Guttural whimpers] Struggling under his colossal weight... he is unable to right himself.

He can only watch... as the rival takes his place at the female's side.

[Guttural moaning] For a dinosaur of his size, a badly damaged leg could mean the end of the road.

♪ So could a Lusotitan survive this kind of injury?

♪ Francisco: OK, I'm going down to find the track.

Pedro: OK. Narrator: On the coast, a significant piece of evidence might provide the answer.

But reaching it won't be easy... ♪ because what was once flat ground during the Jurassic is now a near-vertical cliff face.

Hi, Francisco, we are in position.

We can see you so you are ready to go.

[Metal clanking] Narrator: Francisco must descend over 300 feet.

OK.

I'm ready.

I am going down.

♪ Hi, Francisco.

How are you?

♪ Hey, Pedro.

I am in the upper part of the track now.

I can see several footprints and this part of the tracks seems to be very well-preserved.

Narrator: Etched into the cliff face are footprints thought to have been made by a large Lusotitan.

♪ And they reveal something surprising.

Francisco: The length that there is between the footprints is one meter and 97 centimeters.

OK, I got it.

Narrator: One stride is less than 6 1/2 feet.

The right stride is two meters and 7 centimeters.

Narrator: The other is closer to 7.

We have a clear difference between the right and left stride.

So, Francisco, we have a difference of about 10 centimeters from the right and left stride.

The foot and the hands are OK but this animal is not walking normally.

Probably because he is limping.

♪ Narrator: The discovery of a limping Lusotitan is important evidence.

It suggests that injuries to their enormous limbs were survivable.

♪ Even so, Old Grande is still weak... and won't last long on a damaged leg.

But he does have a remarkable way to speed up the healing process.

[Crunching] It's known as osteophagia.

[Gulps] Like modern-day giraffes, he supplements his diet... [Heavy stomp] [Burps loudly] by breaking apart and swallowing the skeletons of dead animals.

Like the carcass of this Pliosaur, whose bones are rich in the minerals he needs... to repair his own body.

[Guttural whimpers] But he's still a long way from recovery and a limp like his may not have gone unnoticed.

♪ Following the path of the Lusotitan footprints, something has caught Francisco's eye.

From my position, I'm--I'm pretty sure that there is several other footprints also on the cliff.

Do you think you can approach the position?

Francisco: OK, I am going to try it.

Narrator: The second set of prints is another 250 feet down the sheer cliff face.

No, I can't do it.

Very difficult to go down and take a look more closely.

Narrator: Unable to reach the prints by land, the team decides... [Waves crash] to take to the air.

[Drone whirring] Pedro: OK, Francisco, we send the drone up.

The footprints are just to my right.

Whoa, whoa, whoa.

I think... Oh.

See?

Pedro: It's very clear.

Elisabete: Yeah.

Oh, my gosh.

Elisabete: And it is so close to the other track way.

Narrator: The second set of prints follows the same path as the Lusotitan.

But from their distinctive shape, it's clear they've been made by a different species.

Pedro: You have the middle finger.

It's very large.

Elisabete: Yep.

Very different from the other prints that are rounded.

So this could be a potential predator to the Lusotitan.

It's a medium to large size theropod, clearly.

Narrator: Theropods are a group of dinosaurs that includes T. rex.

But on this island, the prints are likely to come from a predator... Old Grande would be much more familiar with.

[Waves crashing] The Torvosaurus.

30 feet long and nearly 10 feet tall, this adult female would normally be no match for a healthy Lusotitan.

But the pain in Old Grande's leg has become unbearable.

And he must rest until he can recover.

It could mean days without food or water... leaving him exhausted... and vulnerable.

[Huffing] [Grumbling] An opportunity this big... is rare.

But Old Grande is too strong to take on now.

So she's prepared to stay close... and wait.

♪ As the days pass, Old Grande rests.

[Snoring] ♪ [Growling] The Torvosaurus risks an approach.

[Light footsteps] [Ferocious growl] A close call.

[Deep growl] Old Grande must recover soon, because next time, he may not be so lucky.

♪ ♪ [Guttural growl] ♪ At long last... Old Grande's leg is finally on the mend.

[Deep chitter] And he has unfinished business... finding the female that left him behind.

♪ But both she and his rival are now miles away and the clock is ticking.

♪ He must move as quickly as he can.

150 million years later, the team has made a discovery that could reveal how fast a giant like Old Grande traveled.

Francisco: It's particularly interesting because it's a fragment of the scapula that is part of the shoulder.

We have also the humerus.

We have the ulna.

So we have the arm.

Narrator: The new find gives the team an almost complete profile of Old Grande's front limb.

Pedro: So we have here more or less 6 feet for the humerus and 6 feet for the scapula.

Narrator: Putting these measurements together with their findings from the cliffside footprints... Francisco: His stride is around 6 1/2, uh, feet.

Narrator: They can now calculate his speed.

We can estimate that this animal can walk from 4 to 5 miles per hour.

This is really interesting.

Narrator: It may sound slow, but like modern elephants, it's thought Lusotitans could keep up this pace over huge distances.

♪ [Soil crunching] This is just what Old Grande needs to do... as he travels miles across the island... looking for the female.

But he's almost out of time.

[Thunder rumbles] A distant storm... heralds the arrival of the seasonal rains.

[Grumbles] [Thunder clapping] The female will finally be ready to mate... leaving Old Grande in danger of missing out to his rival.

[Heavy stomp] But he's not just relying on his pace alone.

He's using an extraordinary ability to locate the female.

[Heavy stomp] One he's thought to share with modern-day elephants.

His stomps send powerful seismic waves through the ground.

[Birds chirping] [Huffing] Many miles away, she feels the earth move... through specialized nerve endings in her feet.

And she answers... [Heavy stomp] her suitor's call.

Detecting her response... keeps Grande heading in the right direction.

[Thunder rumbles] But he must reach her before he misses his chance.

[Huffs] [Tapping with hammer] At the dig site, a new section of Old Grande's bones is emerging from the rock.

So perhaps, this is-- this is the first one, sure.

Probably this is the second one.

Narrator: Including fossils that belong to his giant tail.

-Like that?

-Yeah.

I would say this one would be... That's bigger.

Narrator: But laying them out from the biggest on the right to the tip on the left... Pedro has noticed something unusual.

Everything should belong to the same individual.

If we compare all these tail bones here, this seems to be smaller.

Narrator: One of the bones doesn't belong in the sequence... and it's too small to be part of Old Grande.

So I think we have two individuals in this quarry.

I would say we have another smaller adult.

Francisco: Amazing.

Narrator: It's a significant find... because a second adult so close to Old Grande... could mean he did find his mate.

[Birds chirping] ♪ After miles of walking... he's reached the area where the female last responded to his call.

[Growls] [Foot thuds] [Birds chirping] [Deep growl] [Heavy stomp] [Distant bellowing] ♪ Reunited at last.

[Distant growling] But the moment... is short-lived.

[Ferocious growling] The rival male has stayed close.

And he isn't going to give up without a fight.

[Growling] [Thunder clapping] [Guttural growling] Each bull uses his colossal weight... as a battering ram.

♪ But these giants are too closely matched... so changing tactics... [Snarls and growls] they use their teeth... to inflict intense pain.

[Snarls and growls] But neither is backing down.

Taking his chance, the rival pins Old Grande.

[Guttural moaning] Rearing up to the height of a 4-story building... [Guttural growl] he bears down with his enormous weight.

But this time... Old Grande refuses to go down.

[Thunder claps] [Hoarse breathing] [Deep growl] A decisive victory.

[Distant bellowing] But Old Grande still faces one last challenge.

Persuading the female he really is the bull for her.

[Drill vibrating] And it could be that Francisco has discovered the key to what made Old Grande irresistible.

I can recognize that we have this group of bones here that are very close and are one touching the other.

Narrator: It's a series of disc-shaped vertebrae that once formed part of his long neck.

Francisco: It's not complete, but it's particularly well-preserved.

Structurally, it's very delicate.

Narrator: The bones are incredibly fragile... so the team covers them in a protective membrane.

We need to glue all these small cracks because if we take out the vertebra, we can lose the bones completely.

Narrator: But these neck bones are not delicate simply because of their age.

Each one has a hollow structure which may have served a vital purpose.

Pedro: These animals are huge giants of the Jurassic.

They have very long necks, huge tensions, and stress.

So one of the probable advantages of having these hollow bones is that this helps the animal to be lighter and more dynamic in the movement of these huge necks.

Very useful.

[Tapping with hammers] Narrator: This dynamic movement would have allowed Old Grande to walk, fight, and, crucially, display.

[Growling softly] It's exactly what he needs to charm the female.

Because he hasn't won her over yet.

[Whimpers] [Heavy stomp] Like many birds today, it's thought he would use his long, lightweight neck and flexible tail in an elaborate courtship display... ♪ with every move he makes carefully assessed by this most discerning of judges.

And she responds.

[Stomping] Staying in sync with each other's moves will be crucial to proving they're compatible.

But just as everything was going so well... Old Grande gets a little overexcited.

[Grumbles then huffs] Fortunately, he has one last trick up his sleeve.

Just like modern birds, such as frigates... Old Grande may have had an inflatable sack to attract attention.

♪ It seems to have worked.

[Soft purring] ♪ And in the hills of Central Portugal, Pedro, Elisabete, and Francisco have also completed their mission... finishing this year's dig with a treasure trove of fossils.

Francisco: This is a very good season.

We have a lot of new things this year.

Pedro: 200... Francisco: 256.

Some of them are really large bones.

Narrator: Even as they pack up, they're already making plans to return next year.

It's interesting to try to find more bones of both individuals.

Here there is more areas to explore.

Man: Tienes calor?

Man 2: Una que puede funcionar bien, eh?

Narrator: While they may never know how Old Grande met his end... his bones appear to be entwined with a female Lusotitan.

♪ And so just maybe with her, he was able to secure his legacy.

[Growling softly] A batch of giant eggs.

♪ [Birds chirping] [Soil rustles] ♪ Buried safely beneath the ground, this next generation of Lusotitans... [Egg cracking] will soon begin their own story.

♪ [Growling] Narrator: Lusotitan was a towering dinosaur that ruled Portugal in the late Jurassic, 150 million years ago.

Known only from partial remains, it has rewritten the record in European paleontology and posed a major mystery.

[Soil rustles] This Jurassic long-necked titan is almost identical to dinosaurs found in the United States... despite the two countries being separated by thousands of miles of ocean.

So what was it doing here?

The most recent discovery of this colossus was made in the quiet Portuguese town of Pombal.

And it's given experts their most complete picture yet of this island giant.

Its remains are now being stored at a local school... [Device whirring] where paleontologist Elisabete Malafaia is examining them in more detail.

And one stands out from all the others-- a newly discovered enormous rib.

When we start to excavate the ribs, the rib continue and continue and the, since that, this rib never end, and for the late Jurassic theropods this is the largest rib, that we know in the world.

More than 7 feet.

Narrator: The sheer size of these bones... cement Lusotitan as one of Europe's largest dinosaurs.

But its features bear a striking resemblance to Brachiosaurus... another colossal, long-necked, 40-ton goliath that roamed the western United States.

[Deep growling] [Screeches] It's part of the sauropod family, which also includes the titanic Diplodocus and Brontosaurus.

Brachiosaurus appears to be closely related to Lusotitan.

[Branch snaps] And it's this connection that has puzzled scientists for years.

It's a mystery that has only deepened with another remarkable discovery.

Housed at the Natural History Museum in Lisbon is the near-complete skeleton of an iconic American predator... also unearthed in Portugal.

Allosaurus... a theropod and relative of T. rex.

[Ferocious growls] Allosaurus is one of the most common theropod dinosaurs... in North America, but not in Portugal.

This specimen was the first evidence of Allosaurus outside North America.

Narrator: The discovery of a Portuguese Allosaurus was the first time one single species of dinosaur was found in both America and Europe.

When it was unearthed, it amazed dinosaur experts across the world.

Along with Lusotitan, it led paleontologists to examine all the fossils discovered in Portugal for intercontinental relatives.

We discover other dinosaurs such as Stegosaurus.

[Snarls] We have also Torvosaurs, we have Ceratosaurs.

We have almost the same dinosaurs we know in North America.

Narrator: With so many dinosaur species appearing on both sides of the Atlantic... [Grumbles] it's led to an intriguing theory.

Elisabete: This suggests that during the late Jurassic, the land masses were connected by land bridges when these dinosaurs lived.

Narrator: Though America and Europe were once a single land mass, by the start of the Jurassic, they had been split by the newly formed Atlantic Ocean.

But Elisabete thinks these land bridges could have continued to connect the two continents for millions of years.

Elisabete: Land bridges could allow the dinosaurs to cross between what is now North America and Portugal.

Narrator: The Atlantic Ocean would eventually expand further, and with rising sea levels, these land bridges would be lost beneath the waves.

But they may ultimately be the key to solving the prehistoric mystery of how Portugal became home... to the colossal Lusotitan.

[Bellowing] ♪