The UnXplained

Monstrous ancient beasts

who once roamed our planet

lay hidden beneath our feet...

apocalyptic disasters

that transformed prehistoric Earth...

and cutting-edge technology that could one day

resurrect the dinosaurs.

Stegosaurus,

velociraptor, triceratops

and the mighty Tyrannosaurus rex.

It's intriguing to think that, millions of years ago,

colossal creatures reigned supreme on our planet.

And while scientists have been studying the giant fossils

of what we call "dinosaurs" since the early 1800s,

the fact is, we know very little

about these extraordinary beasts.

What more can be revealed

about the existence and extinction

of the most baffling behemoths to ever roam the Earth?

Well, that is what we'll try and find out.

It's funny to think that a group of long-extinct,

incomprehensibly massive "giant lizards"

are as beloved to us as a puppy dog.

Today, dinosaurs are an enduring fixture in popular culture,

but what do we really know

about these extraordinary, diverse creatures

who have captivated our imagination for centuries?

Dinosaurs are a hugely fascinating group of animals

for a massive chunk of humanity.

It's like people of all groups,

all nationalities, all ages...

from young kids to old people...

everyone's interested in dinosaurs.

I mean, the whole idea that there's a group

of often gigantic reptiles that lived millions of years ago,

is one of the key things

that makes us really interested in them.

I think dinosaurs are central

in the collective social imagination now

because they hint at the existence

of a full and complete alien Earth

that none of us experienced.

When we discovered "them,"

the giant lizards, something totally different

than the life we have today,

well, that has a mystique to it that just doesn't go away.

But we really, ultimately, don't know much

about the dinosaurs and the world they inhabited.

The first dinosaur to be excavated

that was named would be Megalosaurus,

and this was described in 1825

by William Buckland, an early paleontologist.

And at the time, they thought it was a bear-like creature.

They didn't really know that Megalosaurus

was a dinosaur then because the concept of "dinosaur"

had not yet been invented.

That fell to another paleontologist, Richard Owen,

working at the British Museum in London,

who recognized that animals like Megalosaurus

were a completely new group of reptiles

that he named "Dinosauria."

Today, every week or so,

new dinosaurs are being discovered.

There are so many species

being discovered, you literally can't keep track of them.

I think the latest count is something between

1,300 and 1,400 known species,

and dozens of new species are found every year.

Assuming dinosaur diversity was roughly comparable

to modern large mammal diversity,

that would suggest that something like

a quarter of a million species might have existed.

Dinosaur fossils have been found

on all seven continents.

Paleontologists have unearthed giant, lumbering herbivores...

swift, two-legged predators,

monstrous creatures that roamed the ocean depths

and flying reptiles that were the size of a fighter jet.

And despite everything we've uncovered,

these creatures are still one of Earth's greatest mysteries.

The Field Museum of Natural History, Chicago, Illinois.

Every year, more than a million people come to see

the museum's most popular attraction,

the most remarkable Tyrannosaurus rex skeleton

ever found,

a fossilized monster affectionately called Sue.

Sue the T. Rex

is the most famous fossil in the world.

It's famous because it's the most complete

adult T. Rex that has ever been discovered

in 120 years of T. Rex research.

And we have about 73% of the bones,

so 280 of the 350 bones that make up the skeleton.

Sue was first found near Faith, South Dakota, in 1990.

It was found by Sue Hendrickson

and a team of commercial paleontologists

that were looking for fossils.

This is one of the biggest,

most powerful land predators that's ever existed.

It has a total length of roundabout 13 meters.

It would have weighed roundabout ten tons.

Tyrannosaurus rex has an incredibly broad,

hugely powerful, very heavily muscled skull

and its teeth are rounded and cross-sectioned.

They're more like... kind of like railroad spikes.

This dinosaur was able to take among the most powerful bites

of any land-living animal in history.

So, it is an awesome animal.

It makes perfect sense that people

are really obsessed with this incredible animal.

Scientists have estimated

that there was once two and a half billion.

T. Rex dinosaurs on Earth.

Yet, so far, we've only found about 30

relatively complete skeletons.

And this astonishing low percentage of discovery

can be applied to many other species

who have laid buried for millions of years.

I'm sure that humans have been tripping over dinosaur bones

for thousands of years,

but they weren't recognized as fossils.

The oldest known dinosaur that we can see right now

is a dinosaur from Tanzania that is called Nyasasaurus.

It's about 237 million years old.

But we don't know the total number of dinosaurs

that ever existed and probably never will.

If we go back to the turn of the last century,

to, say, 1900,

there was one new dinosaur species discovered

and published about every year.

By 1970, it was half a dozen.

Now it's one a week.

I would guess that we haven't even come close to discovering

one percent of the dinosaur species that ever lived.

And then there are certain environments

that just don't preserve geologically.

For example, there were probably alpine dinosaurs.

Think of today's mountain goats and bighorn sheep.

Well, mountains erode.

In order to form fossils, you need places

that collect sediment, not places that shed sediment.

So, there are, there are just some dinosaurs

that we will not discover, I think, ever.

There's a huge

amount of diversity out there waiting to be found.

And sometimes, we find something that completely surprises us,

that kind of overturns our thinking.

One of the strangest out there is there's an animal

called Yi qi, from China...

and it has these bat-like membranous wings

it could fly on.

But the absolute strangest dinosaurs,

in my mind, would have to be the alvarezsaurs.

And I described one of these animals,

a little animal called Albertonykus.

They have these incredibly short forelimbs,

but they're very stoutly built,

and they had a single hooked claw.

They'd take these claws, rip into logs,

rip into termite nests,

and put their long, little snout down there

and eat the insects.

So, dinosaur anteaters. In my mind,

that's the strangest thing they ever came up with.

Paleontologists have unearthed

all kinds of bizarre dinosaur species,

including Spicomellus,

an armored tank with spikes fused directly to its ribs,

and Deinocheirus,

a massive omnivore that combines traits

from several different branches of the dinosaur family tree.

Yet, there are countless questions

that remain unanswered.

We are still just scratching the surface.

We only know a tiny percentage

of the things that we would like to know and which we could know.

There's a massive wealth of dinosaur finds

still yet to be made.

What kind of animals dinosaurs were like when they were alive,

what their social behavior was like,

how they interacted with one another,

exactly what they looked like

and exactly what they did with their appearances,

how they interacted with one another

during, like, mating displays.

We know almost nothing.

The evolutionary relationships of dinosaurs,

when they evolved, where they evolved, when they went extinct,

a lot of these things we still need to understand.

How are all these various species related?

How is a T. Rex related to a brontosaurus,

related to a triceratops,

and the... related to a velociraptor?

Because if we had a complete evolutionary tree,

we could see when certain link groups appeared

and where they appeared and how their anatomy evolved.

It would help us piece together their evolution

in a far more complete way.

And we're trying to build something like that,

but it's incredibly difficult,