[Gentle music] ♪ [Insects chirping] ♪ Bertie Carvel: Over 66 million years ago... [Deep, guttural growl] our world... [Dinosaur screeches] was ruled... [Shrieking] ...by dinosaurs.

[Soft growl] ♪ [Growling] 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... [Shrieking] and they... can walk again.

[Ferocious growl] ♪ [Theme music playing] ♪ [Car passing] Utah.

In the heart of the American West.

♪ Home to some of the most spectacular and other-worldly scenery on Earth.

♪ And the forces that shaped the landscape also make it a paradise for dinosaur hunters.

♪ In a remote part of the desert, paleontologists Jim Kirkland and Josh Lively have made a remarkable discovery.

Josh: So we've exposed quite a bit of bone.

Jim: Yeah, I agree.

♪ Carvel: The bones of one of the most heavily armored dinosaurs that ever lived.

Josh: Oh!

That's cool.

Carvel: A Gastonia.

Jim: Yeah, you might have a leg there.

Carvel: Using their discoveries, we can imagine how this youngster lived and died... ♪ 130 million years ago.

♪ In the early Cretaceous period... the land that will become Utah was warmer and wetter.

♪ [Birds chirping] And what is desert today is covered by conifer forests and rolling meadows of ferns.

[Birds chirping] ♪ [Low growling] ♪ Plentiful food... for groups of plant-eating Gastonia... [Whines] including youngster, George.

♪ [Guttural grunt] Like all young Gastonia, he must stick close to his parents... [Munching] because danger... is never far away.

[Utahraptor chitters] [Utahraptor hisses] Utahraptor.

[Screeches] [Hissing] A heavyweight cousin of Velociraptor, the size of a grizzly bear.

♪ And they hunt vulnerable young Gastonia.

♪ The ferns providing ideal cover for a surprise attack.

[Gastonia snorts] [Crunching] Just yards away, George and his family are oblivious to the approaching danger.

♪ With the raptors within striking distance, the Gastonia get a lucky break.

[Twig snaps] [Growling and screeching] [Low, guttural growling] Like many modern herd animals, the adults form a defensive ring around their young.

[Screeching and growling] Weighing over a ton each, covered in thick armor, a group of adult Gastonia is virtually invulnerable.

[Screeching and growling] [Utahraptor hisses] [Low, guttural growling] [Utahraptor chittering] With one of their group injured, the raptors cut their losses.

♪ [Crunching] But George can't rely on the safety of the herd for much longer.

He's reaching adolescence when, like all young male Gastonia, it's thought he'll be pushed out of the group.

[Dinosaur growls] George must now grow up without his family to protect him.

♪ [Metal scraping against rock] Man: We'll probably do Dakota and at least one other person, too.

Carvel: At the dig, the team is starting to uncover evidence... Man: Is there a bone there coming up from somewhere?

You wanna get your fingers under that if you can reach over.

Carvel: that might explain how young Gastonia like George survived to adulthood.

Josh: You got one over there.

Man: There's a big guy here, this.

Oh, OK, looks like a limb bone.

Might connect to some of this bone right here.

Carvel: And the clues are coming thick and fast.

Man: Beautiful!

That's bone.

Looks like the rib might go into this one.

Carvel: Everywhere they dig, bone after bone emerges from the ground.

Found a couple of ribs right here going over top of a vertebrae, then several pieces of armor.

A ton of bones just in this small spot.

Carvel: It's too many to be from just one individual.

Got these thin rib-like sections.

Right.

I mean, so far you know, right in here there's probably parts of two animals.

Carvel: And intriguingly, all the Gastonia found across the site appear to be of a similar age.

Man: From looking at skeletal remains, we're looking at half-grown individuals, you know sub-adults to full adults Josh: Kind of analogous to teenagers, right?

Jim: Yeah.

Carvel: All these teenagers found together suggests something unexpected.

♪ [George squeaking] [Growls] Since leaving his family group, George has been living on his own... [Guttural huff] keeping deep in the forest where it's easier to hide from predators.

[Grunting, hissing] [Water rushing] ♪ But it's not long before he comes face to face with another young male.

[Guttural growling] And it looks... like he means business.

[Thud] [Low, guttural growling] ♪ Gastonia's skulls and necks are specially adapted to act like shock absorbers.

♪ [Low, guttural growling] But this isn't a fight.

♪ This is how Gastonia make friends.

[Deep growl] ♪ Of all the armored dinosaurs... [Low, guttural growl] they're one of the only known social species.

George has just joined a group.

♪ It's a huge step forward, dramatically increasing his chances of making it to adulthood.

♪ This gang of teenage boys will stay together until they're tough enough to fend for themselves.

♪ Because until their armor is fully developed, they're vulnerable.

[Rocks scattering] Just working our way around these elements, try to get around this big femur here.

Carvel: At the dig, amongst the Gastonia bones... Hey, Josh.

Check this out.

What is that?

Carvel: the team makes an unexpected discovery.

Oh, wow.

That's really neat.

It's definitely not Gastonia.

[Indistinct chatter] Josh: Hey, Jim.

Jim: Yeah?

Heather found something interesting and I'm wondering if you could tell me whether or not it is what I think it is.

Got a nice curve... Yeah, that's a small therapod metacarpal end bone, could be a juvenile Utahraptor.

♪ Carvel: Utahraptor bones found alongside the young Gastonia... All right.

I was right.

It's a therapod metacarpal.

Man: Yeah, confirmed.

Carvel: suggests that throughout the Gastonia's adolescence... [Jim laughing] Utahraptor was an ever-present threat.

♪ [Hammer tapping stone] And Josh and Jim have evidence that shows just how deadly they could be.

A cast of a Utahraptor toe claw.

You know, you put the claw itself, you know this is the bone underlying it.

Just to be conservative, we could say it comes out to about there-- Yeah.

you know, in length.

Carvel: A foot long, these killing claws were Utahraptor's primary weapon.

This thing might be kicking through inch-thick hide so fast you can barely see it.

Wam, wam, wam, wam.

This thing's just punching lots of holes which would do a lot of damage.

Carvel: These claws are the perfect tool for puncturing the weak armor of young Gastonia.

Maybe you have to think of it more as a can opener.

Yeah, if it can flip it over, use that to slice open the belly.

Yeah, these things are one of the most formidable predators that ever lived.

♪ Carvel: Holding their toe claws off the ground to keep them razor sharp... ♪ [Utahraptor chitter, hisses] Utahraptor... [Chitters] is a finely tuned killing machine.

♪ [Ferocious screeching] And this adult male... [Bleating, hissing] and the group he leads have just entered the forest... [Gastonia snorts] following the trail of George and the Gastonia gang.

♪ [Munching] ♪ But hidden beneath the thick undergrowth... [Ferocious screech] finding them won't be easy.

♪ [Huffing] So the young raptors streak ahead... [Utahraptor chittering] to try and flush them out... ♪ [Huffing] while the adults follow behind ready to make the kill.

[Crunch] [Grunt] ♪ With Utahraptor's eyesight as sharp as modern birds of prey, even the slightest movement could be fatal.

[Screeches] [Huffing] So, when they hear the raptors coming... [Distant screeches] the Gastonia freeze.

♪ [Low growling] ♪ [Utahraptor squawks] [Utahraptor chitters] The juveniles have missed them.

[Shallow breathing] But George must hold his nerve because the deadliest threat is still to come.

[Utahraptor grumbles] [Sniffing] The group leader.

♪ [Utahraptor screeches] [Guttural grunt, hissing] ♪ [Growls] [Footsteps receding] [Relieved growl] It's a close call.

♪ [Deep growling] But every day George and the gang survive is a day closer to the safety of adulthood.

[Low, guttural huffs] ♪ And emerging from the ground, clues that reveal even young Gastonia would have been no pushover.

[Puffs air] Ah, well, you should be getting close, I think.

Hey, Josh.

In my section, tell me what you think.

Josh: So... Man: There's so much here, plenty of osteoderms.

Josh: And they're coming out pretty solid then?

Man: Yeah.

Carvel: Osteoderms are the bones that made up the Gastonia's armor.

That's a real nice one.

Oh, yeah.

So you can kind of see on this one that kind of ridge right there, that keel that would point up.

Makes for a spikey dinosaur.

It really does, yeah.

Carvel: In life, each osteoderm was covered by a thick scale.

Now, this is-- it's one of the nicest ones we've had so far.

This would have been on the back of the animal.

Carvel: Which would have created an armored plate.

Where you see the hollow base that these have, they're for blood vessels, bringing nutrients up into this bone to grow that big scale that was on top.

There's a lot of armor on these animals.

Carvel: It's a discovery that reveals the Gastonia's armor was nearly fully formed... ♪ [Engine revving] ♪ but the team has evidence Utahraptor was one step ahead.

[Garage door rattling] Revealed by an astonishing fossil found near the site and taken to the lab for analysis.

Ah, it's a gold mine.

It really is.

Carvel: Entombed in this 9-ton block of sandstone, the team has discovered the remains of an entire group of Utahraptors.

And over here we've got the string of articulated vertebrae.

Yeah, and then that's just beautiful.

Carvel: And hidden amongst the hundreds of perfectly preserved teeth and claws and bones... Yeah, that's the great thing about this block.

We'll have so much material.

Carvel: curator Don Dablue has found something that could be Utahraptor's deadliest weapon.

We got this beautiful little top of a skull, and then we flipped it over.

Right here is the impression of the brain.

Carvel: For a dinosaur, this young Utahraptor brain is very large.

Jim: Yeah, certainly remarkable given the size.

Yeah, that would be a very intelligent animal.

Don: They would have been the most intelligent animal of its time.

Oh, certainly.

Utahraptor would have been capable of some pretty complex behaviors.

[Insects chirping] ♪ Carvel: Spring has turned to summer.

♪ [Grunting] ♪ And as the dry season sets in, George and the Gastonia gang leave the forest to find water.

[Low, guttural growling] ♪ They're still unruly teenagers... ♪ but now with almost fully developed armor.

♪ [Low, guttural growl] [Gulping] And at the edge of the waterhole, clay-rich soil provides the gang with essential minerals... vital for strengthening their armor.

♪ And now the Gastonia are tougher, they're no longer an easy kill.

So the raptors change tactics.

[Gastonia growling] The group leader attracts their attention... [Hissing, screeching] and uses his brightly colored wing feathers [Growling and screeching] to create... a diversion.

-[Utahraptor growls] -[Gastonia grunts] ♪ [Guttural cries] ♪ Like a fox in a henhouse, the kill triggers the leader's predatory instinct.

[Ferocious screech] [Heavy snorting] Trapped at the water's edge, it looks like George's luck has run out.

[Guttural cry] ♪ Man: Yeah, I think you're right.

Get to the tracking, absolutely.

Man: Yeah, and then once we have the track on the back... Carvel: But at the dig, Josh and the team have made a discovery.

They've come to retrieve a fossil that may shed light on events that happened here 130 million years ago.

Josh: So, Don, I was originally thinking it was down this drainage but looking at it now I actually think it's further over that way.

Don: Yeah, I think you're right.

Carvel: But collecting it from the steep cliff face...

Damn, this is gonna be tough.

Carvel: won't be easy.

♪ Don: It might be further that way.

That's... ♪ Josh: Oh!

There it is.

Yeah, that's totally it.

Yeah.

So, Don, I think if you wanna bring the back board over here and then we can go ahead and start strapping it down.

Man: With your legs.

Woman: Do it.

Carvel: This is a fossiled foot cast.

Man: Man on campus.

Josh: All right.

You got it, Marcello?

Marcello: Got it.

♪ Carvel: It formed when a dinosaur footprint filled with silt and dust but over millions of years was compressed into solid rock... Like that.

OK. Just like that.

Luckily, it's not super fragile.

Carvel: creating a cast of the foot that made it.

♪ Marcello: All right.

1, 2, 3.

Woman: It definitely gets easier up here.

Marcello: OK. OK. Carvel: But which dinosaur does it belong to?

♪ The strap [indistinct].

A little more slack.

Marcello: Wow.

That's really cool.

We've got 3 big wide toes on this footprint, so that eliminates a couple dinosaurs right off the bat.

Yeah.

A sauropod would be... Carvel: If it was Gastonia, it would have 4 toes.

So, a big rounded track.

And it's unlikely to be a predator because there are no claws.

Woman: Most likely a plant-eater.

Man: Yeah, I think a good candidate could be some sort of bipedal plant-eating dinosaur kind of like Planicoxa.

Right, we're at the right level for those guys, or close.

Absolutely.

Carvel: Planicoxa were beaked stocky dinosaurs that lived in herds.

You can imagine them traveling together and moving long distances.

For sure.

Don: Maybe Gastonia was year-round and these dinosaurs were more seasonal.

♪ Josh: All right.

You guide us, Steph.

Steph: OK. Carvel: Finding Planicoxa footprints here is an important discovery... ♪ because it suggests they migrated through this landscape.

[Low, trumpeting call] ♪ [Dinosaur bellows] As the group leader closes in on George... [Utahraptor screeches] [Low, trumpeting call] a herd of Planicoxa pass close by.

[Dinosaur bellows] [Utahraptor chitters] And without any armor, they're a much easier kill.

[Planicoxa grunting] ♪ handing George... [Utahraptor chitters] a very lucky escape.

[Low, trumpeting call] But as the dry season intensifies, the Planicoxa herds will move on.

[Birds chirping] [Low grumbling] So as George and the Gastonia gang return to the forest, they know it won't be long until the raptors are hunting them down once more.

[Birds chirping] [Grass rustling] ♪ But coming out of the ground... Marcello: All right, let's see how long this is.

Carvel: further evidence the Gastonia are buried here... We're looking at about just over 1 foot long.

Carvel: Were more than capable of defending themselves.

And the proximal width, where it attaches to the tail, just under 7 inches.

Steph: Yeah.

Josh: So, yeah, this is a one of these specialized spikes along the tail.

Steph: Like sticking out?

Yeah, yeah, so it'll be sticking out from the sides of the tail.

You can imagine this with a big scale over top of it, a bit piece of keratin, so this would have come to a very sharp point.

And these we think were used as a weapon.

♪ Carvel: These blade-like spikes were positioned along the entire length of the Gastonia's tails.

♪ And Jim and Don have uncovered something that shows just how these weapons were used.

And then as I was trying to work on that, I hit something over here.

So this is a femur, the upper leg bone.

That's a pretty sizeable femur.

And then as I dug around, I see we have a complete tibia, lower leg bone.

Yeah.

You can see how short, you know, the lower leg is, of the upper leg.

About half the length, right?

Which is, you know, exact opposite than what you see in a running animal.

Carvel: Gastonia had a top speed of around 5 miles per hour, because their hind legs weren't built for running.

They were adapted for a very different purpose.

Man: Certainly these things are not just simple bones.

They have huge muscle attachment points, so they've developed powerful legs for serious strong maneuverability.

Don: Stocky guys just standing their ground.

You just see these things just holding on the ground and swinging their tail with those big blades, just like the one over there they already pulled out.

Yeah, that big boy.

Yeah.

Slashing across and probably reach head high easily and literally slap a Utahraptor you know, right in the face.

Carvel: Gastonia's powerful hind legs and spiked tails... [Gastonia grumbling] mean George and the gang have quite the defensive arsenal.

♪ [Running footsteps] ♪ But with the dry season now at its height and the Planicoxa gone... the raptors are starving.

♪ Desperate for food, they must take any opportunity... [Hisses] [Gastonia bellowing] to make a kill.

[Guttural snorts] ♪ [Utahraptor screeches] But now nearly fully grown, the Gastonia gang will stand and fight.

[Gastonia growling] [Ferocious screeches] [Growling and screeching] ♪ And this time, they've got the weapons to hold the line.

[Growling and screeches] ♪ The Gastonia now have the upper hand.

♪ But driven by hunger, the raptors have no choice but to attack.

[Ferocious screech] ♪ [Low, guttural growl] with the group leader fatally wounded... [Utahraptor chitters] the remaining raptors back down.

♪ [Low, guttural growl] But George's moment of triumph will be short-lived.

[Low, guttural growling] ♪ The hot summer months bring a new danger... ♪ something revealed by a completely different type of evidence found alongside the Gastonia bones.

♪ Paleobotanist Carol Hotton is an expert in ancient pollen.

♪ Jim: Howdy, Carol.

Carol: Hey, Jim.

Take a look.

There's some interesting grains right in the center.

Soif you see those little round grains that look like flat tires, that's pollen from an extinct conifer.

And there's another grain.

That's a member of the Cyprus family that was well-adapted to dry conditions.

♪ Carvel: All the pollen Carol has identified belongs to trees that lived in a parched, arid environment.

♪ 130 million years ago, the forest that covered the dig site was a tinder box.

You can see all through the field black pieces.

Yeah, little shards.

Yeah, little, little shards.

Twiggy-looking things, except they're pretty small for twigs.

Right.

In all probability, they represent charcoal.

It's unlikely to be anything else, and I see that in all my pollen samples.

Carvel: There's only one thing that could have produced so much charcoal.

♪ The long, dry summer months have created a time bomb.

[Thunder clapping] [Flames crackling] ♪ As wildfire rages through the parched forest... ♪ [Guttural snorts] it threatens the Gastonia and the surviving raptors.

[Utahraptor screeching] ♪ [George growls] But George is slow to react to the danger.

[Fire crackling] [Low, guttural cry] ♪ [Utahraptor screeches] ♪ [Utahraptor screeches] ♪ With a top speed around 20 miles per hour, the raptors soon reach a clearing in the forest.

♪ [Utahraptor screeches, hisses] But they're trapped between the flames and a treacherous marshy swamp.

[Utahraptors screeching] ♪ And George and the Gastonia gang aren't far behind... [Weak grunting] ♪ the flames driving the two mortal enemies together.

[Screeching cry] for one final... [Screeching cry] showdown.

♪ [Snorting] ♪ Oh, that's so nice.

Beautiful claw... Carvel: But back at the lab... You see--oh, that's just a little femur.

Carvel: the sandstone block filled with raptor bones... Jim: And then this one here... Carvel: has one last secret to reveal.

Marcello: And nice little jaw right there.

Oh yeah, I see the teeth on that.

Amazing thing is that all these delicate little teeth are all still in place in their sockets.

Oh, it's really remarkable to have it so well-preserved.

Carvel: Such high levels of preservation... Hard to tell.

And certainly this, you know still has the teeth included.

Carvel: tell the team the bones have not been disturbed.

The block captures the very moment the raptors died.

And interesting that all the best-preserved bones all seem to be in this sand.

Yeah, suggests that sand is part of why they died, why they're so well-preserved.

Carvel: Although the sand is solid today, Jim believes that when the raptors died, it was liquid.

You know what killed them is what buried them.

Given the geology of the setting, most likely we're looking at a mass mortality tied to quicksand.

♪ [Flames crackling] Carvel: Perhaps George and the Gastonia gang got another lucky break.

♪ [Tree creaking] ♪ [Utahraptor growls] [Tree thuds, flames crackling] [Utahraptor screeches, chittering] ♪ Panicked, the raptors run into trouble.

[Utahraptor chittering] ♪ [Screeching cry] ♪ [Flames crackling] With the raptors out of the way, George has the chance to escape... ♪ [George grunts] ♪ [Gastonia growls] but they're struggling.

The very things that protected them from the raptors-- [Gastonia growls] heavy armor and short stocky legs... ♪ [George gasping] mean George and the gang are too slow to escape the fire.

[George gasping] ♪ One by one... the smoke takes its toll.

[Gastonias gasping] ♪ [Loud thud] ♪ Buried where they fell, the landscape is transformed around them.

♪ Layer upon layer of rock builds up... as the eons pass and the continents silently drift across the face of the Earth... ♪ until George and the gang are finally found... 130 million years later.

♪ ♪ [Hisses] ♪ Utahraptor is the largest species of raptor that ever lived.

[Screeching] But until relatively recently, no one knew this fearsome predator even existed.

♪ [Ferocious screech] ♪ In the early 1990s, paleontologist Jim Kirkland was working in the Utah desert when his team discovered a huge claw belonging to an unknown dinosaur.

Jim: Well, when I first saw this claw, you know, I got real excited.

We need to find more of this animal.

This is something new and it is huge.

Carvel: Jim thought it might belong to a new species of raptor... [Puffs air] but to be sure, he needed more evidence.

Then in 2005, he got the lucky break he needed.

Jim: A geology student reported some dinosaur bones coming out of the base of a cliff.

And we went up and excavated.

We found it was such a dense accumulation of bones, you couldn't put an ice pick in without hitting something.

[Machinery rattling] Carvel: So many bones so close together meant the team had to take them all out in one huge slab.

[Rattling] Jim: We ended up having a 9-ton block filled with skeletons.

Carvel: After nearly a decade of excavation, they finally got it back to the lab... Jim: Lift and fold.

Carvel: and could begin to uncover what was inside.

Jim: There's more therapod material than anything I've ever seen.

Yeah, this thing, at least 95% meat-eating dinosaur bones.

Carvel: The first bones to emerge all belonged to small dinosaurs.

One more here.

OK. Carvel: But deeper into the rock, the team began to find much larger bones.

We pulled a big tibia out of there with the ankle in place.

We have part of an adult tail here, more of the base of the tail right there, but big adult animal.

And those bones are stout and massive.

Carvel: Jim had finally found the dinosaur his mysterious claw belonged to.

Jim: So this thing is built like Arnold Schwarzenegger.

It's anchoring massive muscles with foot-long blades on their feet and 4- and 5-inch hooked raptorial claws on their hands.

[Screeching] Carvel: Named Utahraptor, it's 16 feet in length.

But with most raptors the size of a turkey, how did Utahraptor get so big?

♪ Jim thinks the answer could be linked to a little-known extinction event at the end of the Jurassic.

Jim: We're putting together a new story that shows a major extinction in Earth history that hadn't really been recognized before.

We lose 3 major groups of large predatory dinosaurs, the kings of their creation, they all go extinct.

♪ Carvel: For reasons no one fully understands... [Growls] big carnivores like Torvosaurus and Allosaurus completely disappear from this part of North America.

Jim: Other animals do survive elsewhere but in this region, we have nothing.

It's almost a total wipeout.

Carvel: But the extinction of one species creates opportunities for the survivors.

With all the large predators gone, there was a gap at the top of the food chain.

My baby.

Carvel: And over millions of years, Utahraptor evolved to take over... Jim: There's this niche open, you know, no-one is filling it, these things just got real big to take advantage of the hole in the landscape.

Carvel: Transforming into a new and terrifying top predator.

Jim: The Utahraptor liked to stalk in the brush.

The prey has no clue they're there till they were in striking distance.

And as soon as they did it, it would flex open its arms, you know, and leap, screaming at its prey.

It would happen so quick.

When you look at a lion attack or a leopard attack-- Bam!

They're on it.

[Utahraptor growls] [Gastonia grunts] That's how Utahraptor would be, too.

Carvel: A fortuitous find in the desert and an evolutionary lucky break gave us the largest raptor that's ever lived.

♪ Next time... T. rex's lethal, faster cousin.

[Growls] ♪ [Dinosaur shrieks] A young hunter fighting for her place in the most ferocious pack on Earth.

[Growling] [Theme music playing] ♪