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In the depths of space,

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a threat is looming.

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Trapped between the orbits
of Jupiter and Mars…

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the asteroid belt.

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One and a half million chunks
of ancient rock,

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circling the sun.

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Drifting endlessly.

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But, in a single moment of pure chance…

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…one asteroid is thrown out of its orbit.

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A fleeting instant,

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millions of kilometers from Earth,

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sends it on a new trajectory

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towards the very center
of our solar system.

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But its journey will come
to a sudden and violent end,

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in one of the most catastrophic events
in Earth's history.

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And the final chapter

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in the epic story

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of the dinosaurs.

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It's three million years

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since the asteroid
started its journey towards Earth.

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And the dinosaurs rule the planet.

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They dominate the land
and are now entering the ocean as well.

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The high sea levels
have split North America in two…

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creating endless coastlines…

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hundreds of tropical islands…

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and opportunity.

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But these islands are no paradise.

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They are home to a formidable predator.

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One of the fastest,
most agile dinosaurs of its kind.

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North America's answer to the Spinosaurus.

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Just not in the way you would think.

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Not even remotely.

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This is Hesperornis.

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He is formidable, and he is fast.

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But he's pretty much the opposite
of his giant, terrifying cousins.

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He's awkward…

37
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…and clumsy.

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And has tiny teeth.

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Not exactly the traits
of a ferocious hunter.

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But what he does share with Spinosaurus

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is that he's not confined to dry land.

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In fact, he's the most advanced
aquatic dinosaur in history.

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Like some sort of prehistoric penguin,

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he's able to swim far out to sea
to access feeding grounds

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that were previously out of reach.

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This is the bounty of his new blue realm.

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Down here, his big clumsy feet
become powerful propellers.

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And his 94 needle-sharp teeth
snatch fish with ease.

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But as an air-breather,

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he's still tied to the surface.

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And the surface
is not a safe place to linger.

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Because below,

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there are beasts

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twice the size of a killer whale.

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Mosasaurs.

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The apex predators of these seas.

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Hesperornis must get back to the shore.

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But the mosasaur moves
with frightening speed.

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Luckily, Hesperornis is much more agile.

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But he's exhausted.

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Which gives the mosasaur one last shot.

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Hesperornis is a true survivor,

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venturing further into the ocean
than any dinosaur ever has.

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But these waters are treacherous,
even for the best swimmers.

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Despite the dinosaurs' success
in the shallows,

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the mosasaurs

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rule the waves.

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Eight hundred miles north, on land,

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it's a different story.

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Fueled by a warm, stable climate,

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the dinosaurs' dominance here
is unrivaled.

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The great sauropods
are thriving among the tall trees,

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as they have
since the dawn of the Jurassic.

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But down below,
there has been a revolution.

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A female hadrosaur.

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While she may be dwarfed
in present company,

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she's actually larger than an elephant.

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And she won't be held up by these giants,

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because nothing can stop
a mother on a mission.

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And that mission

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is to feed her family…

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who are somewhere

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down there.

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Long ago, their cheek-stuffing ancestors
were scarce and scattered.

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But hadrosaurs are now so successful,
their herds are thousands strong.

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The greatest gatherings of dinosaurs
the world has ever known.

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But this female's family
isn't traveling with the herd.

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There, in the safety of the crèche,

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a sprawling nursery
for hundreds of young hadrosaurs…

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…including her own.

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At six months old,
they have insatiable appetites,

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and will eat
almost anything she brings them.

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Anything.

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Feeding in this bird-like way
takes a lot of refills,

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so she's constantly leaving
to go find food.

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And when moms are away,

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little ones will play.

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With the wingspan of a fighter jet,

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pterosaurs are now bigger than ever.

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And crèches are
the perfect hunting grounds,

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where unguarded nests
are the easiest pickings.

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Despite the threat
from this towering monster,

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the mothers will defend their babies
at all costs.

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But the giant pterosaur
is determined to feed.

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The screams from the nest
are like a dinner bell to the predator.

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But the little ones
aren't just crying in fear.

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They're calling for help.

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This fierce instinct
to protect their young

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is central to
the hadrosaurs' remarkable success.

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But other dinosaurs
are taking defense to a whole new level

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because the arms race
between predator and prey is escalating.

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And this will give rise
to the most iconic dinosaurs of all time.

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This will take so long

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that the continent
of North America will shift,

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the land buckling up into the sky.

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The Rocky Mountains.

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It's here, in the foothills below,

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that the dinosaurs are making an impact.

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Pachycephalosaurus.

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Using their outrageously thick skulls…

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to duel for supremacy.

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And alongside them,

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a dinosaur
with even more impressive headgear.

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Triceratops.

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She may look like a rhinoceros,

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but she's twice the size of one.

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And armed with spear-like horns
over one meter in length.

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Triceratops and Pachycephalosaurus
have impressive weapons.

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Yet there are some here

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that are even more armed and dangerous.

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Under the cover of darkness,

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the latest and greatest
of the armored warriors.

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Six meters long and highly territorial.

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Ankylosaurus magniventris.

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He's on patrol for intruders

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bold enough to breach his borders.

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His tank-like torso is covered
in dozens of thick, bony plates.

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And what's more,

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he has a powerful new weapon.

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A club-like tail, weighing half a ton,

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that he can use to take on
whatever stalks these forests.

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He senses something.

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His borders have been breached…

144
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by the worst possible intruder of all.

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A Tyrannosaurus rex.

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Ankylosaurus

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versus T. rex.

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An evolutionary stalemate,

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millions of years in the making.

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But in this arms race,

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there's one thing
that does set these dinosaurs apart.

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Intelligence.

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T. rex is one of the most
fearsome predators of all time.

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And to remain at the top of her game…

155
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…she must eat the equivalent
of 200 steaks every day.

156
00:24:35,307 --> 00:24:40,562
And yet, so far,
she hasn't eaten a single bite.

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00:24:43,565 --> 00:24:49,154
That's because she has special plans
for this take-out meal.

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But Ankylosaurus is no light snack.

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00:25:05,712 --> 00:25:08,423
Six tons of muscle and bone,

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with an assortment of lumps and bumps.

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Even for T. rex,

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it's quite a drag.

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Finally,

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her journey's end.

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And the reason
she's gone to all this effort.

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Five hungry hatchlings.

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A ferocious killer,

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yes.

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00:26:56,364 --> 00:26:57,824
But also,

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a devoted mother.

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She will ensure

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her little ones are well-fed…

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to give them the very best start in life.

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Something their distant ancestors

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could only dream of.

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Far back in the Triassic,
tiny Marasuchus hatched into hell.

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00:27:50,168 --> 00:27:53,046
These dinosaurs-in-the-making,

178
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forced to live in the shadows.

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Hiding from the ruling reptiles.

180
00:28:03,890 --> 00:28:06,184
But when fate intervened…

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they turned catastrophe

182
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into opportunity…

183
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and began their monumental rise.

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Growing bigger, stronger,
and ever more formidable.

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00:28:34,212 --> 00:28:35,463
In time,

186
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they would triumph, not just on land,

187
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but in the sea

188
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and the sky.

189
00:28:47,976 --> 00:28:51,020
After 160 million years,

190
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the dinosaurs are now so dominant…

191
00:28:56,818 --> 00:29:00,321
…nothing on Earth can stand in their way.

192
00:29:06,828 --> 00:29:09,539
But something not of this Earth

193
00:29:10,123 --> 00:29:11,332
will.

194
00:29:13,209 --> 00:29:17,922
Because as this family's journey
is just getting started,

195
00:29:19,215 --> 00:29:20,675
another journey

196
00:29:21,176 --> 00:29:23,344
is approaching its end.

197
00:29:27,932 --> 00:29:34,522
The asteroid, now hurtling towards Earth
at 50 times the speed of sound,

198
00:29:36,024 --> 00:29:40,028
will finally have its date with destiny.

199
00:30:13,561 --> 00:30:18,483
It smashes into the ocean
off the coast of Mexico,

200
00:30:19,234 --> 00:30:23,613
with the power of a billion atomic bombs.

201
00:30:24,823 --> 00:30:27,951
Temperatures are hot enough
to vaporize the seabed…

202
00:30:30,995 --> 00:30:35,667
along with every living thing
for hundreds of kilometers.

203
00:30:44,676 --> 00:30:48,096
Far away, in the foothills of the Rockies,

204
00:30:49,055 --> 00:30:55,144
these great dinosaurs
have no idea what's about to hit them.

205
00:31:17,125 --> 00:31:20,795
The largest earthquakes in history.

206
00:31:29,596 --> 00:31:32,307
But the worst is yet to come.

207
00:31:35,602 --> 00:31:41,065
An enormous wall
of superheated debris explodes outward.

208
00:31:58,499 --> 00:32:03,254
The dinosaurs
caught beneath this death cloud

209
00:32:03,338 --> 00:32:05,465
are entombed.

210
00:32:08,051 --> 00:32:13,222
Their world is so hot,
it literally bursts into flames.

211
00:32:22,357 --> 00:32:24,442
Even the toughest armor

212
00:32:24,943 --> 00:32:26,778
is no protection.

213
00:32:36,162 --> 00:32:39,749
The cloud quickly engulfs
the entire planet,

214
00:32:40,249 --> 00:32:42,418
suffocating it with ash.

215
00:32:44,504 --> 00:32:46,923
Shrouding it in darkness.

216
00:33:32,844 --> 00:33:37,890
The few still standing
at the end of the day

217
00:33:39,642 --> 00:33:41,602
are in a nightmare.

218
00:33:43,104 --> 00:33:46,399
Choking in the gloom.

219
00:34:12,675 --> 00:34:14,218
By nightfall,

220
00:34:14,886 --> 00:34:20,475
the death toll
for the dinosaurs is catastrophic.

221
00:34:47,668 --> 00:34:50,338
Starved of the sun's rays,

222
00:34:50,838 --> 00:34:54,759
an impact winter descends on the Earth.

223
00:35:01,140 --> 00:35:05,937
Global temperatures drop
by 25 degrees Celsius.

224
00:35:09,148 --> 00:35:15,363
Conditions too cold
for almost any dinosaur to withstand.

225
00:35:27,041 --> 00:35:29,460
Giant sauropods,

226
00:35:29,961 --> 00:35:31,671
laid to rest

227
00:35:32,171 --> 00:35:37,677
in the cinders of the very trees
that made them so tall.

228
00:35:53,484 --> 00:35:55,778
In their crowded colonies,

229
00:35:56,529 --> 00:35:58,614
those who live together,

230
00:35:59,407 --> 00:36:00,950
die together.

231
00:36:08,708 --> 00:36:12,295
Protective mothers
cannot shield their young

232
00:36:12,378 --> 00:36:14,505
from the freezing temperatures.

233
00:36:20,636 --> 00:36:24,765
The punishing cold has also taken its toll

234
00:36:25,391 --> 00:36:28,728
on the most famous dinosaur of all.

235
00:36:37,528 --> 00:36:39,530
The Tyrant King

236
00:36:40,448 --> 00:36:41,866
has fallen.

237
00:37:01,802 --> 00:37:05,223
Even the mighty Tyrannosaurus rex

238
00:37:05,848 --> 00:37:08,351
will not survive this.

239
00:37:40,007 --> 00:37:42,551
The reign of the dinosaurs

240
00:37:44,095 --> 00:37:45,721
has finally

241
00:37:46,514 --> 00:37:48,474
come to an end.

242
00:38:17,003 --> 00:38:20,298
But 66 million years later…

243
00:38:22,717 --> 00:38:26,262
the dinosaurs are rising again.

244
00:38:30,891 --> 00:38:32,268
This time,

245
00:38:32,351 --> 00:38:34,270
at our hands.

246
00:38:42,028 --> 00:38:47,908
Today, their fossils stand
as monuments to a lost world.

247
00:38:49,076 --> 00:38:50,411
But more than that,

248
00:38:51,787 --> 00:38:58,210
they are the keys that unlock
the secrets of the dinosaur story.

249
00:39:00,004 --> 00:39:04,884
Our understanding of their lives
is now greater than ever.

250
00:39:06,302 --> 00:39:08,471
From their very first moments,

251
00:39:09,638 --> 00:39:11,265
to their very last.

252
00:39:15,019 --> 00:39:20,024
And the revelation
that on Earth's darkest day,

253
00:39:20,608 --> 00:39:23,361
not all dinosaurs died.

254
00:39:25,363 --> 00:39:30,743
Some were small enough
to find shelter from the apocalypse.

255
00:39:33,496 --> 00:39:35,373
And survive

256
00:39:36,040 --> 00:39:38,459
even to this day.

257
00:39:40,961 --> 00:39:46,384
The flying dinosaurs
we now call the birds.

258
00:39:50,846 --> 00:39:56,936
And the clues to their past
are hiding in plain sight.

259
00:40:18,416 --> 00:40:24,588
The remarkable journey
that started 235 million years ago

260
00:40:25,798 --> 00:40:29,427
continues alongside us.

261
00:40:31,554 --> 00:40:33,722
They are the last remaining link…

262
00:40:36,016 --> 00:40:38,644
to a long-lost kingdom

263
00:40:40,646 --> 00:40:42,231
that was

264
00:40:43,232 --> 00:40:44,733
the age

265
00:40:45,526 --> 00:40:47,445
of the dinosaurs.