♪ [Insects chirping] ♪ Bertie Carvel: Over 66 million years ago... ♪ [Wings flapping] [Deep, guttural growl] our world was ruled... [Triceratop growls] by dinosaurs... [Dinosaur bellows] ♪ [Dinosaur shrieks] the largest animals that have ever walked the Earth.

♪ 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... ♪ can walk again.

[Ferocious growl] ♪ ♪ 3.5 million square miles of parched sand... the Sahara Desert is one of the most inhospitable environments on Earth... [Sand rustling] [Car engine revving] but for dinosaur hunters like Nizar Ibrahim, it's a gateway to a lost world.

♪ [Generator running] ♪ Deep in a remote part of the desert known as the Kem Kem, Nizar and his team are excavating the remains of one of the largest predatory dinosaurs that ever lived.

♪ Man: Is it broken there?

Ibrahim: I don't know.

It seems to be one bone here and one here.

Wow.

♪ Carvel, voice-over: A Spinosaurus.

Ibrahim: Oh, it's, beautiful.

What do you reckon?

Man: Maybe a rib?

A rib?

Yeah.

I knew we'd find one.

[Tool whirring] Carvel, voice-over: Using the team's discoveries, we can imagine how it lived and died 100 million years ago.

♪ ♪ In the late Cretaceous period... ♪ Africa has just broken away from South America... ♪ and the land that will become the Sahara... ♪ is a river system.

♪ Its waters support acres of scrub and forest that provide shade from the intense Cretaceous sun... [Birds chirping] ♪ perfect for an afternoon nap.

♪ [Snoring] ♪ This is Sobec, the Spinosaurus... [Snoring] ♪ 36 feet long, his powerful jaws packed with teeth.

♪ Disturbing this monster's sleep could have deadly consequences... [Baby Spinosaurus squawking] [Grumbles] ♪ [Snapping] ♪ [Growling] ♪ [Dinosaur squealing] [Dinosaur squawking] ♪ but this isn't a snack.

♪ It's one of his babies.

♪ Sobec is a new dad.

[Squawking] Like some species of modern birds, once the eggs are laid, the job of looking after the kids falls to him.

♪ [Baby Spinosaurus squeals] ♪ [Baby Spinosaurus squeals] ♪ Sobec must keep his young family alive until they can fend for themselves.

♪ [Jackhammer tapping] ♪ A hundred million years later... Man: Looks like bone.

Ibrahim: You got the location mark all right?

Carvel, voice-over: Nizar and the team are starting to uncover evidence that could shed light on how Spinosaurus raised their young... Ibrahim: See more?

Any luck on that side?

Carvel, voice-over: bones that show Sobec wasn't built like other dinosaurs.

Ibrahim: So Marco can see this nice, little curvature here.

I think this is certainly a vertebrae.

It's a little fragile, this one.

Carvel, voice-over: This vertebrae was part of Sobec's 20-foot tail.

Ibrahim: All right.

let's get it out, and let's see if we can find more.

♪ Carvel, voice-over: In total, the team has recovered more than 40 tail bones... Woman: This will be vertebrae number 22.

Yep.

OK.

Starting from the smallest one?

So you're starting distally.

Yes.

Carvel, voice-over: and for Nizar and fellow paleontologist , Francesca Borchi, they reveal something unique.

♪ What I think is really remarkable is, like, you get close to the tip of the tail and you still have these really long spines.

Carvel, voice-over: Spines like these are not found on the tail bones of other predatory dinosaurs.

Once you see the shape of the spines, it's quite narrow...

Yes.

and flat.

Basically just a giant paddle.

Yeah.

The more we collect, the more aquatic this thing becomes.

♪ Carvel, voice-over: For Nizar, a thin, flat tail can mean only one thing.

♪ Spinosaurus was a swimmer.

♪ Underwater, Sobec is in his element, using his huge tail to power him through the water.

♪ He's guarding a nursery pool, the place he and his babies call home... ♪ [Baby Spinosaurus squawking] and with dad's back turned, the kids take to the water.

[Squawking] ♪ This secluded backwater is the perfect kiddie pool.

[Croaking] [Wings flapping] ♪ So while Sobec's patrolling, the babies hone their hunting skills... ♪ but it's not long before one of them gets into trouble.

♪ If it doesn't get help soon, this baby will drown.

♪ [Birds chirping] ♪ Dad... to the rescue.

[Baby Spinosaurus squawking] ♪ [Squawking] ♪ [Insects chirping] ♪ With everyone safely back on the bank, the family settles down to sleep... ♪ but they must soon leave the safety of the nursery pool and travel somewhere Sobec knows they can catch far more substantial prey... ♪ but they'll be running a gauntlet fraught with dangers... ♪ because, although the dig site is barren and lifeless today... ♪ Nizar and the team have evidence that when Sobec was alive, the Kem Kem was far more perilous.

Lots of big, predatory fish.

There's a nice jaw, absolute monster.

Carvel, voice-over: Its rivers teemed with massive, carnivorous fish... Borchi: Ah, this is nice.

Carvel, voice-over: and enormous crocodiles.

Look at that.

OK.

Tip of a snout, right?

This is where the nose end is essentially.

This will be the size of the biggest crocs today, like nasty Elosuchus.

Carvel, voice-over: Elosuchus is an extinct species of croc with jaws 4 feet long.

This tooth is very nice, still here.

Yeah.

They're pretty robust.

♪ Carvel, voice-over: If the rivers were dangerous... Ibrahim: Carcharodontosaurus tooth.

Carvel, voice-over: the land was home to an even more deadly predator.

Man: Yes.

It's very well-preserved.

I can see all of the serrations here.

Ibrahim: Like a steak knife, right?

Carvel, voice-over: Carcharodontosaurus was the T. rex of Africa, 10 foot tall and armed with more than 50 flesh-cutting teeth.

Ibrahim: Got several T. rex-size predatory dinosaurs or even bigger than T. rex-- big crocs, giant fish.

Not very safe.

Ibrahim: Yeah.

You know, there are really many different ways to die.

♪ Carvel, voice-over: These lands were once home to more large predators than anywhere else in Earth's history... ♪ a fearsome collection of carnivores that Sobec must navigate if he's to feed his family... ♪ and there's danger lurking at every turn.

[Baby Spinosaurus squawking] ♪ Hidden from view, the murky waters are patrolled by at least 8 species of ferocious crocodile... ♪ but that's the least of their worries... [Bush rustles] because the family has just entered the territory... ♪ [Huffing] of Carcharodontosaurus.

♪ This fearsome, 6-ton killing machine is also on the hunt for food.

♪ [Gulping] ♪ [Grumbles] [Alanqas screeching] [Wings flapping] [Munching] [Sobec growls] [Ferocious growling] ♪ Time to get the babies to safety.

♪ [Growls] ♪ With so many deadly predators around, it will take everything Sobec's got to reach his destination without his family becoming someone else's meal... ♪ [Car engine revving] ♪ ♪ and not far from the dig site, on a remote plateau... ♪ the team has discovered signs of another monster... Ibrahim: You good?

Man: OK good, I'm ready to go whenever you are .

Carvel, voice-over: evidence that's best seen from the air.

[Drone whirring] ♪ Ibrahim: So how many pictures are we taking in total?

Man: About 500, 600.

♪ So if we start down that ridge and then work our way over and do that whole site... ♪ Carvel, voice-over: The photographic survey reveals what's hidden here.

♪ Arranged in rows, these aren't just boulders.

They're footprints.

♪ This is a dinosaur trackway... ♪ [Wings flapping] and to identify which dinosaur made it... Really big one.

Whoa.

Carvel, voice-over: Nizar and colleague Roy Smith take a closer look.

You got this edge here and then quite a nice shape around that side, as well.

Yeah, very nice.

Carvel, voice-over: Each footprint is a cast of the foot that made it...

So the claw over there, right?

Yep, yep.

I think there's two more there.

Yeah.

The back of the foot.

Yeah.

Carvel, voice-over: and at over 3 feet across, they're some of the biggest ever found.

No.

This is really impressive.

There's a bit missing, or it would have been even bigger.

It would have been even bigger.

We've got a giant here.

Yeah.

Yeah.

Carvel, voice-over: These footprints were made by one of the largest dinosaurs that's ever lived-- ♪ Titanosaurs, huge long-necked dinosaurs 65 feet high.

♪ At more than 60 tons, each one weighs as much as a herd of elephants... ♪ [Loud, trumpeting call] [Heavy, slow breathing] ♪ but for one elderly member of the group, this has become its final resting place... ♪ [Birds chirping] ♪ [Growling] ♪ and it could provide Sobec with the food he needs... [Growls softly] for his hungry babies... [Huffing] [Squawking and squeaking] ♪ but they're not the only ones on the lookout for a free lunch.

♪ An adult Carcharodontosaurus... [Ferocious snarl] [Screeching cry] has already laid claim to the carcass.

♪ With his babies to look after, Sobec can't risk injury... ♪ so he must now decide if it's a prize worth fighting for.

[Growling and wailing] ♪ [Snapping] [Growling] ♪ Sobec is bigger... ♪ but one bite from these jaws could be fatal.

♪ [Growling] Sobec's fearsome claws could give him the advantage... ♪ but, crucially, the Carcharodontosaurus... ♪ is built for hunting on land... ♪ [Growling] ♪ [Hisses] so Sobec backs down.

[Birds chirping] ♪ His family won't eat today... ♪ but if they can survive their journey, a much bigger prize awaits.

♪ As night falls, Nizar and the team examine an astonishing fossil.

♪ Ibrahim: The place where this was found, it was so narrow, you could only just, um, crawl on your belly, essentially.

Carvel, voice-over: Discovered close to the dig site, it's the remains of an extinct species of fish.

♪ Ibrahim: This is the head of Onchopristis.

The brain case, the blade-shaped snout, it's all there.

♪ Carvel, voice-over: Onchopristis is commonly known as a sawskate because of the long snout lined with barbs it used to stun its prey... Ibrahim: This would have been a fairly slow, bottom-dwelling skatelike animal.

OK.

But that's insane.

♪ Carvel, voice-over: and with Spinosaurus so at home in water, Nizar has a theory.

Ibrahim: So this would have been one of the primary food sources for Spinosaurus.

Incredible.

God, it's amazing.

Wow.

♪ [Insects chirping] Carvel, voice-over: Sawskate could grow up to 13 feet in length... ♪ so a single fish would make a sizeable meal... ♪ but once a year, like rays do today, it's thought they gathered to breed... ♪ in their thousands... ♪ providing an incredible feast... ♪ that awaits Sobec and his family... ♪ [Huffing] [Squawking] but in this predator-invested land, danger can strike at any time... ♪ [Alanqa screeches] [Wings flap] ♪ [Hammer tapping] ♪ and 100 million years ago, there weren't just predators on land and in the water.

They were also in the air.

Ibrahim: So this is a lower jaw of a Alanqa.

This is a Kem Kem pterosaur.

It is a pretty remarkable specimen.

Man: Uh-huh.

Carvel, voice-over: Alanqa was a huge, flying reptile with a 23-foot wing span, ♪ twice that of any bird alive today.

♪ Essentially, what we're looking at here is, the skull would be going back, you know?

Like this.. Yeah, something like this.

more or less.

Yeah.

Pretty big.

Yeah.

It's probably the largest Kem Kem pterosaur.

♪ Carvel, voice-over: Its jaws reveal what this flying monster would have eaten.

It's got this really interesting raised structure here that's got, like, a Y shape.

There's a corresponding matching part in the upper jaw, and so maybe this was something that was used to crush hardshell prey.

♪ Carvel, voice-over: Although it's adapted to eat shellfish, Alanqa was so big, it didn't need to be picky.

♪ It's possible that these things were catching little things on the ground, you know, when they walk on the ground.

Maybe little dinosaurs, little crocs, amphibians, whatever they could catch.

Yes.

Yes.

♪ Carvel, voice-over: With Alanqa about, no small creature was safe.

♪ [Alanqa screeches] ♪ [Wings flapping] ♪ [Deep screeching] ♪ [Footsteps] To reach the sawskate breeding ground, Sobec must lead his young family through the forest.

♪ It's their final challenge... [Huffing] but the most deadly.

♪ ♪ [Squawks] [Light footsteps] ♪ [Alanga growls softly] ♪ For Alanqa, a young Spinosaurus would make a tasty meal... [Squeaking] ♪ and the dense foliage provides perfect cover... ♪ for an ambush.

[Squeaking] ♪ [Twigs breaking] [Sobec growls] ♪ [Steady breathing] ♪ [Squeaks] ♪ [Steady breathing] ♪ [Baby Spinosaurus squeals] [Sober grunts] Too late.

[Ferocious growling] ♪ Having come so far, losing one of his babies is a huge blow... ♪ [Growls softly] [Baby Spinosaurus squawking] but if Sobec is to keep the others alive, he must keep moving.

♪ As the family emerges from the forest... ♪ their journey's end is in sight-- ♪ the sawskate breeding ground... ♪ and the promise of plentiful food for Sobec and his family... ♪ but for his babies to eat, Sobec will have to fight his way to the front of the queue... ♪ [Hammer tapping] ♪ [Indistinct conversations] ♪ and at the dig, Nizar and paleontologist Gabriele Bindellini have evidence that could reveal how Spinosaurus settled their differences.

♪ Ibrahim: So I think this is the tallest we've got.

Bindellini: Mm-hmm, and it still miss a good portion at the tip.

♪ Yeah.

I mean, I think we're missing 30... Mm-hmm, 30, 40.

35, maybe even 40 centimeters.

Mm-hmm, Which makes it super long.

Yes.

Do you want to take this end?

I'll hold it here.

Mm-hmm.

Carvel, voice-over: About 5 feet long, this is one of the 15 bones that rose up from Sobec's back supporting his enormous sail.

♪ I've tried to visualize all of his other spines.

I mean it's a massive structure.

♪ Carvel, voice-over: Spinosaurus sails are so big, they must have had an important function.

It's probably, like, primarily a display structure to, you know-- To be seen from the distance.

Yeah, like-- Peacock.

Yeah, like a peacock's train.

Carvel, voice-over: But unlike a peacock, Nizar believes the main function of Spinosaurus' sail might not have been to find a mate.

Ibrahim: So you want Spinosaurus, and you come close to another Spinosaurus' territory and what are you gonna see?

You're gonna see this big sail, right, and just by looking at the sail, you can go, like "Ooh, that's a really big Spinosaurus, I better not get close to this guy."

Stay away from here.

I think it would be very efficient at scaring off other predators or rivals.

[Shovel scraping] ♪ Carvel, voice-over: Sobec's intimidating sail could be just what he needs to win a prime fishing spot.

♪ Having run the gauntlet of Kem Kem predators, there's now only one thing standing between him and feeding his babies-- ♪ a rival Spinosaurus.

[Growling] ♪ [Roaring loudly] ♪ Sobec must try to intimidate this older male and take his place on the bank... [Growling] ♪ so he initiates a ritual dance... ♪ showing off his sail... [Growling] ♪ but as a young male, Sobec's sail is smaller... ♪ [Low, guttural growl] ♪ and not intimidating enough.

[Ferocious growling] ♪ [Squawking] Forced from the bank, where the fish are easier to catch, the job of feeding his hungry babies... ♪ has just got much more difficult.

[Water sloshing] ♪ [Hammers tapping] ♪ Ibrahim: Can we get some measurements?

Marco?

♪ Carvel, voice-over: But evidence from the dig... Marco: 140.

Carvel, voice-over: suggests Sobec may have been well-equipped for the challenge.

[Camera shutter clicks] Ibrahim: It's something we haven't really seen before, something new.

Man: Yeah.

One of the missing foot bones.

Yeah.

Carvel, voice-over: Sobec's foot bones are similar to those of water birds, meaning his feet could have been webbed... Ibrahim: Here we are.

Maybe then we're going to wrap it in this, tape it.

This one we're going to put in a plaster jacket.

Carvel, voice-over: helping him to swim after his prey... [Indistinct chatter] Where's the box?

Carvel, voice-over: and if he caught it, Sobec had another adaptation...

The teeth are really amazing.

Carvel, voice-over: that made him a formidable underwater predator.

Borchi: If I didn't know Spinosaurus was here, I would say this is a crocodile tooth.

Looking at it, the shape is basically the same, you know?

Carvel, voice-over: Unlike the broad, blade-like teeth of other predatory dinosaurs, Spinosaurus teeth are smooth and conical, like a crocodile's because they both eat the same food.

♪ Ibrahim: This is basically your main piece of anatomical weaponry if you're going after fish, those really big fish, stabbing slippery prey.

Carvel, voice-over: With more than 60 of these teeth in its long jaws... ...but it's conical.

Carvel, voice-over: Spinosaurus was able to tackle the largest fish.

♪ Imagine having to hold on to a big sawskate, fighting for its life.

Yeah.

It definitely wasn't an easy catch.

Yeah.

I mean, they put up a real fight.

You need these kind of killing tools, right, to hold on to the prey.

Carvel, voice-over: Webbed feet and spikey teeth are critical adaptations that Sobec will need to make a catch... ♪ but even so, success... ♪ is far from guaranteed.

♪ Although Sobec is faster, the sawskate is more agile.

♪ Time for a change of tactics-- ♪ attacking from below... ♪ like a shark.

♪ [Water splashes] Success... ♪ but getting his catch to his family won't be easy.

[Growling] ♪ [Snarls] ♪ [Wails] ♪ [Growling] ♪ This time, Sobec is in no mood to give up his kill.

♪ [Squawking] ♪ By leading them to this land of plenty, Sobec has ensured his babies' survival... ♪ but his moment of triumph... [Munching] ♪ has come at a terrible cost.

♪ Ibrahim: So these are small parts of the femur, the thigh bone of our Spinosaurus.

Yeah.

Wow.

That's really nice, right?

Carvel, voice-over: Slices cut through Sobec's bones have a disturbing story to tell.

We looked at some of the sections.

We looked at the growth lines under the microscope trying to look at the age.

They came out pretty nice.

You know, it's not as easy as reading growth lines on a tree, but we can narrow it down to an age of 17 to 19 years at death.

OK, so he wasn't that old.

Yeah, like a young adultish, you know.

Carvel, voice-over: Other large predatory dinosaurs are thought to have had a lifespan of about 30 years, but Sobec's bones reveal he was barely an adult when he died.

♪ So maybe he could have lived a little bit longer.

Yeah.

If we assume a similar kind of lifespan for a Spinosaurus, you know, late 20s early 30s, it's a life cut short.

♪ Carvel, voice-over: The evidence hidden within his bones... [Squawking and munching] ♪ suggests Sobec may not have lived to see his family grow up.

♪ In providing for his babies... ♪ he has paid the ultimate price... ♪ [Breathing heavily] ♪ [Breathing heavily] ♪ [Breathing stops] ♪ and as the great river ebbs and flows, it covers his body with layer upon layer of sediment... ♪ preserving Sobec's story beneath the desert's shifting sands... ♪ until he is eventually found 100 million years later.

♪ Spinosaurus is one of the largest meat-eating dinosaurs ever discovered... ♪ [Birds chirping] but it's also the most mysterious... ♪ [Snapping] perhaps the only dinosaur to leave the land behind and take to the water.

♪ Bringing such a weird dinosaur to life is a major challenge for the "Walking With Dinosaurs" team... And then what we can do, Steve, you know the shot that we did on the slider yesterday?

Yeah.

Carvel, voice-over: and it starts with filming the environment it inhabited.

♪ Spinosaurus lived in Morocco 100 million years ago.

[Car engine revving] Stephen Cooter: Morocco today is very much a kind of desert environment, but, in fact, back in the time when Spinosaurus was around, it was much greener, much more of a sort of enormous river system.

Carvel, voice-over: This unique part of southeast Portugal is one of the best matches for the river delta Spinosaurus called home... ♪ So we're here down by this river to film a sequence in the film where the Spinosaurs gather to fish.

This here goes-- Yeah.

♪ Carvel, voice-over: but today, the weather isn't being kind.

Cooter: Might be time to go back to your van.

Yeah I think it's gonna be a bit in and out today, but hopefully, we'll get some sun later on, hopefully.

♪ Carvel, voice-over: Luckily for the crew, the rain soon clears.

♪ Cooter: Good?

Carvel, voice-over: To help imagine the dinosaur action, they use scale cutouts as stand-ins for the digital models.

Cooter: It's a challenge filming things that aren't there, but to try and help us visualize the size and the scale, we've got people with poles, and we've got some tape measures so that we make sure we actually get the dinosaurs in the frame.

They're always sort of a lot bigger than you imagine.

Carvel, voice-over: With the stand-ins in place, the team position the camera to capture the action.

And cue Steve and action.

Neil Harvey, voice-over: Don't think there's any way that we would be walking around this close to these creatures, but actually for this moment, it just feels like the best way to approach it.

You really want to get the camera in there and up close and really feel like you're part of it.

♪ Carvel, voice-over: Once the real-world environments are captured, it's time for Spinosaurus to walk in them, which is tough when you've been extinct for 94 million years... [Growling] so it's over to the visual effects team.

Kirsty Wilson: We wanted to tell great stories, but equally important, if not more important, was making sure we are scientifically accurate, and I cannot tell you the level of research that we went to in this series.

Carvel, voice-over: Our hero Sobec is an entirely computer-generated character, every detail carefully researched and designed from the claws up... ♪ but unlike the other large predators in "Walking With Dinosaurs," Sobec swims.

♪ Daniel Miller: Spinosaurus-- in terms of how it moves, its weight distribution-- we know what it looks like.

What we need to then sell, is how it interacts with the environment.

Carvel, voice-over: And water is particularly tricky to create in the digital world... so back in the field, the team is experimenting with a very unusual piece of equipment-- ♪ a perfect scale replica of a Spinosaurus head.

♪ It's the same color as a blue screen so it can easily be replaced by the visual effects team... ♪ if they can get it to sink.

♪ [Drill whirring] ♪ After practice in the pool, pushing it through the lake creates the hard-to-make splashes and ripples in real time.

[Baby Spinosaurus squawking] Cooter, voice-over: The physical model will create all the water interaction for us.

We can then replace it with our VFX head.

Carvel, voice-over: It gives the animators a huge advantage, letting them blend the Spinosaurus model seamlessly into the real environment... ♪ enabling this strange dinosaur to walk and swim again.

♪ Next time, a gang of armored dinosaurs battles to reach adulthood... ♪ hunted by one of the most fearsome predators... ♪ that's ever lived.

♪