♪♪ [ Tranquil tune plays ] ATTENBOROUGH: The remains of a dragon have just been discovered in the cliffs on the South Coast of England.

It was an enormous marine reptile that ruled the seas at the same time as the dinosaurs ruled the land.

[ Suspenseful music plays ] Scientifically, it's called an ichthyosaur.

♪♪ The bones are so well-preserved, it may be able to give us new insights into the lives of these remarkable creatures.

Together with a team of scientists, we will reconstruct the skeleton and compare it to animals alive today.

[ Squeaking ] We'll try to understand how it looked and how it survived in the open ocean.

Could this be a completely new species of ichthyosaur?

Our search for evidence will lead us into an intriguing forensic investigation into how it died.

MOORE: I think you're lookin' at a 200 million-year-old murder mystery.

ATTENBOROUGH: Solving that mystery will throw light on the extraordinary world of the Jurassic ocean.

♪♪ [ Theme plays ] [ Waves crashing ] ATTENBOROUGH: The story of this extraordinary dragon starts here in Dorset, on the South Coast of England, one of the most important geological sites in the world: the Jurassic Coast.

♪♪ It stretches for almost 100 miles from Devon to Dorset.

♪♪ And it was here that the early geologists first collected evidence that, once, the world was ruled by monstrous reptiles, quite unlike anything alive on Earth today.

♪♪ [ Birds squawking ] Evidence of creatures that existed all that time ago can still be found on these beaches.

Fossil collectors have been coming here for, literally, centuries and these rapidly eroding cliffs are providing them with a continuous supply of exciting things to find.

I started looking for fossils when I was a boy and I've never lost the feeling of excitement and anticipation of what one might discover.

The commonest fossils here are coiled shells called ammonites and you can find them all over the place.

There's one here on this boulder.

You can see the whorls there, but it's mostly been worn away by the sea.

But sometimes, if you're lucky, you can find nodules like this and, if you look at them, you can see there's the edge there of an ammonite and, if I hit it... I'd better put on protective glasses.

If I hit it, it should... [ Laughing ] How about that?

[ Laughing ] Wow!

What a find!

[ Whimsical tune plays ] Ammonites, in fact, are quite common on this beach, but, every now and again, something truly rare and spectacular is found here, and quite often by this man, one of the most skilled fossil hunters I know.

Chris Moore has been collecting fossils here for more than thirty years.

Recently, he came across a boulder which, he thought, might contain something unusual.

Back in his workshop, he exposed a mosaic of small, beautifully preserved bones which he knew straightaway were the front fins, the paddles, of an ichthyosaur.

But they were unlike any he had ever seen before.

♪♪ I still collect fossils.

I even have the remains of an ichthyosaur, a small one, of a kind that's relatively common.

This was collected by Chris about 10 years ago in Dorset.

I never found anything as beautiful as this.

It's got jaws and it's got teeth and it's got paddles.

And Dorset was the very first place where they found a really complete skeleton of one of these creatures.

This is a picture of it, published for the very first time in 1814.

People thought it was some kind of monster, but what was it?

They thought it was a kind of cross between a reptile and a fish, so they called it an a 'fish lizard,' or 'sea dragon.'

[ Suspenseful music plays ] Since that time, many fossil fragments of ichthyosaurs have been discovered on the Jurassic Coast... ♪♪ ...but complete skeletons are very rare.

♪♪ The particular one that Chris has just found is significantly different from any that's ever been found here before.

Chris shows me where he believes the rest of the ichthyosaur's body is: in the cliff, above the part of the beach where he found the paddles.

It's in a limestone layer near the top of the cliff and, to reach it, Chris will have to remove tons of clay.

♪♪ In Jurassic times, sea covered all this area.

On its floor, sediments washed down from the land turned into layers of shales and limestone.

The land rose, the sea retreated, and, now, in the rocks, you can find the remains of the creatures that once lived in those ancient waters.

♪♪ As well as the remains of ammonites, there are the bones of fish, such as sharks.

♪♪ But the top predators at this time were reptiles, ichthyosaurs.

[ Creatures calling ] ♪♪ They dominated the seas for more than 150 million years.

[ Squeaking ] ♪♪ After getting permission to dig, the team clamber down the cliff, to the particular layer where the rest of our ichthyosaur skeleton should be lying.

EXCAVATOR: I'm gonna need at least another meter 'cause I need to drop down to the next bit.

♪♪ ATTENBOROUGH: It's dangerous work: These cliffs occasionally collapse without warning.

[ Rubble sliding ] ♪♪ To make sure that they don't damage any of the fossils, the team do all the digging by hand.

♪♪ EXCAVATOR: There's just loads of roots.

[ Laughter ] ATTENBOROUGH: Tons of clay have to be removed before they even reach the layer of limestone where they hope the rest of the bones still lie.

ALL: Hooray!

[ Laughter ] ♪♪ ATTENBOROUGH: It was on this very same coastline, more than 200 years ago, that the first complete skeleton of an ichthyosaur was discovered.

It was found by a self-taught fossil hunter called Mary Anning in 1811.

It was then, that the popular name sea dragon was given to these prehistoric monsters.

Scientists speculated on how they lived and artists tried to imagine what they must have looked like and how they behaved.

♪♪ Back at the cliff face, Chris and his team are hard at it, but, they haven't found any more bones.

MOORE: This is a massive piece, tomb stone.

MAN: Right, ready.

ATTENBOROUGH: Chris is convinced that the skeleton to which the paddles belonged must be somewhere here, and they check every rock.

MOORE: Beautiful shale.

♪♪ [ Indistinct conversation ] EXCAVATOR: Lovely.

MOORE: Anything interesting?

EXCAVATOR: Moment of truth.

Nothing. -MOORE: [Laughs] MAN: Just push it off. -EXCAVATOR: Yeah.

♪♪ MOORE: Is there showing?

EXCAVATOR: Nothin' obvious.

MOORE: Oh, gosh, that's hard work.

Ooh!

♪♪ I hope there's something here.

I almost don't want to look.

♪♪ MAN: Agh! -MOORE: Ah!

MAN #2: Oh, it's bone. -MOORE: There's a bone.

EXCAVATOR: Loads of bones going all the way.

There's bone there.

MOORE: [laughing] There's something here.

EXCAVATOR: No, it's all the way along.

ATTENBOROUGH: At long last, the team's efforts are rewarded.

MOORE: We've got some bones here!

EXCAVATOR: Oh, yeah. Loads here.

There's loads of bones.

MOORE: Fantastic.

Ah! What's this?

Is that a vertebrae?

ATTENBOROUGH: But the bones are not in the position the team had expected to find them.

Instead of lying the skeleton seems to be bending back into it.

MOORE: We're gonna have to go down through there.

ATTENBOROUGH: It means more work.

And, to make matters worse, [ Thunder rumbling ] a storm is brewing.

MOORE: The rain's just starting, but, I think we've got to make a bit of a run for it.

[ Rain striking ] [ Wind whistling ] [ Thunder rumbling ] ATTENBOROUGH: Rough seas and heavy downpours can cause landslips, which could easily destroy any chance of retrieving the bones.

[ Waves crashing ] It was after just such a storm that Chris found the front limbs, the paddles, of our sea dragon.

convinced him that the fossil was something special.

You can see why when you compare them to the paddles of the kind of ichthyosaur that's usually found here.

MOORE: This is an adult and this is the paddle of this creature and, if you compare it to this one... [ Thudding ] ATTENBOROUGH: Oh, it's huge.

Oh, yeah.

MOORE: I've never seen anything quite like it.

ATTENBOROUGH: There are half a dozen rows of digits there and how many there?

MOORE: I think there's at least 9 or 10, crossways, and, obviously, you know, many more in length.

ATTENBOROUGH: So it's getting on for twice the number of digits.

MOORE: And the whole shape of the fin is completely different.

ATTENBOROUGH: Quite, quite different.

And must be new, therefore?

MOORE: I think so. I've never seen anything quite like it.

ATTENBOROUGH: How exciting.

It's extremely rare to find a new species of ichthyosaur, these days.

Only nine have been discovered here in the last 200 years.

But, can these strange paddles tell us something about how this odd ichthyosaur lived?

To try and find out, we're going to construct a three-dimensional model.

To do that, we first need to have the paddles scanned.

♪♪ To create an image, this cutting-edge scanner takes thousands of X-ray projections through the fossil, in cross sections, as it rotates.

♪♪ It's not long before the first images appear.

MOORE: That's amazing.

It's really clear.

You can even see the bones laying underneath the paddle.

MAVROGORDATO: At the moment, we're just doing one section.

MOORE: Yeah. -MAVROGORDATO: We're going to do more multiple scans down the specimen and build it all back together into a three-dimensional volume.

ATTENBOROUGH: The scans of the paddles are sent to Bristol University.

Here, scientists can isolate the image of each bone within the rock and then assemble them to create a detailed, three-dimensional model.

♪♪ The team is particularly excited by the shape and structure of these paddles, and I've come to find out why.

MOON: We've got a complete paddle here, taken from the bones itself, fully reconstructed, rearticulated, so this is as close as we can get to what it would've looked like.

We can actually start using this paddle to try and tell us what species it might've been.

Because of the size of the paddle and the way that some of these bones articulate with each other, it's different to other and so, this could be a new species.

ATTENBOROUGH: Oh, that would be great.

MOON: It would be jolly exciting.

ATTENBOROUGH: We won't know for sure until we find the rest of the body.

But can the paddles tell us something about the way in which this creature swam?

MOON: There are a lot of bones in this paddle, which would've been good for holding steady and also for allowing it to be maneuverable in the water.

ATTENBOROUGH: There would've been cartilage around that, wouldn't there, somewhere or other? -MOON: Yes.

All of the gaps between the bones would've been filled in with cartilage and even further around the paddle itself, giving it a paddle-like shape, giving it a cross section a bit like an aero foil, so that it could cut straight through the water.

♪♪ ATTENBOROUGH: Could they fold them in to the side?

MOON: Probably not.

Looking at the muscles and where they attach, it suggests these are moving up and down, helping it to turn very quickly or keeping it on the straight and narrow when it wants to be a little more sedate.

♪♪ ATTENBOROUGH: The shape of the paddles and the way they moved seems very like the way an animal alive today uses paddles.

That animal usually lives in tropical waters, like these in the Caribbean.

♪♪ The sea here is warm, with temperatures much like they would've been in Jurassic times around Britain.

And the animal in question is the dolphin.

[ Squeaking ] [ Clicking ] Dolphins, of course, are mammals, not reptiles, like ichthyosaurs.

[ Clicking ] Nonetheless, the two groups have bodies shaped in very similar ways.

[ Squeaking ] The front fins, or paddles, of both would've helped to steady themselves as they turn and cut through the water.

♪♪ And both have similar dorsal fins.

[ Squeaking ] So, although they lived 200 million years apart, dolphins and ichthyosaurs share many physical characteristics and that's because they evolved in similar ways, as a response to a similar environment.

♪♪ Like dolphins, ichthyosaurs evolved from ancestors [ Squeaking ] that had once lived on land.

As they became adapted to life in water, they lost the ability to walk.

Their bodies became more streamlined and their forelimbs turned into paddles, to help them swim.

♪♪ But ichthyosaurs do differ from dolphins in two striking ways.

♪♪ Dolphins have tails that are flattened horizontally and they drive themselves forward by beating their tails up and down.

♪♪ But we know, from their fossils, that ichthyosaur tails were flattened vertically, like those of sharks, so they must've swum in the same sort of way: by sweeping their tails from side to side.

Ichthyosaurs, unlike dolphins, also had back paddles.

They, too, would've helped stabilize them as they swam.

And what's more, the paddles of ichthyosaur are particularly large and long, rather like those of the oceanic whitetip shark.

That shape helps the whitetip to cruise for long distances with very little expenditure of energy in their search for food.

♪♪ [ Calling ] ♪♪ So, it could be that our ichthyosaur was also a long-distance traveler and only an infrequent visitor to the Lyme Regis seas.

Which could be why no one has ever found one of these here before.

♪♪ Back at the dig site, the rain has stopped, at last.

The team must try to extract the rest of the dragon's body before worse weather arrives.

MOORE: That's how hard the rock is.

It's actually smashed the end off the chisel.

So you can see what we're dealing with.

♪♪ ♪♪ ATTENBOROUGH: At last, they find signs of the rest of the skeleton.

MOORE: Lots and lots of bone in there.

MAN: Yeah. -MOORE: Ribs and all sorts of stuff.

ATTENBOROUGH: And there's another, particularly exciting, discovery.

EXCAVATOR: I think it's skin.

MOORE: It's a skin?! -EXCAVATOR: Yeah, look.

MOORE: Oh, really? [gasp] ATTENBOROUGH: They've found signs of fossilized skin.

EXCAVATOR: Rare isn't it? -MOORE: Yeah, very rare.

♪♪ ATTENBOROUGH: The blocks that contain bones and skin can't be thrown down like the other rocks.

They must be carefully strapped up and gently lowered.

♪♪ MOORE: So, first block down, few more to go, but if they go like that, I'll be very pleased.

ATTENBOROUGH: Two weeks after they started work, I go down again to check on progress.

Chris shows me what they've already collected.

MOORE: So, lots over here, with a bit of a wash.

ATTENBOROUGH: Ah, well, I can see something there.

MOORE: Ah! [laughing] ATTENBOROUGH: That's more obvious, yes.

MOORE: Yeah.

Here, you can see, glinting in the sunlight, sections through the backbone, the vertebrae column.

ATTENBOROUGH: Wow!

MOORE: And these are the ribs that are still attached to the vertebrae. And these are the neurals that come off the backbone. -ATTENBOROUGH: The spines off the top of the back? -MOORE: Yeah. Yeah.

But they've actually got skin preserved on them.

ATTENBOROUGH: No, really? -MOORE: Yeah.

ATTENBOROUGH: Can you see that here?

MOORE: Well, that's the very black.

You can see it on the impression as well.

ATTENBOROUGH: This is great news!

But something puzzles me.

Would the head have been on this side or that side?

MOORE: Most likely here, in this next slab.

ATTENBOROUGH: And it's not there?

-MOORE: Not so far -ATTENBOROUGH: Oh boy.

How many more tons to go?

MOORE: [Laughs] ATTENBOROUGH: [Laughs] MOORE: Only a few.

MAN: Okay.

♪♪ ♪♪ ATTENBOROUGH: Once the blocks are down on the beach, the team remove as much excess limestone as possible to make them lighter.

Even then, they're extremely heavy, so to get them back to Lyme Regis, they're loaded onto a pontoon and towed back by boat.

♪♪ ♪♪ ♪♪ So, for the first time in 200 million years our strange ichthyosaur once again takes to the water.

♪♪ ♪♪ The dig may be over, but the investigation is only just beginning.

Now the work becomes more delicate, involving not sledgehammers, but small vibrating chisels that chip off the limestone in tiny flakes.

It's detailed work that will take months to complete.

♪♪ Day after day and week after week, Chris and his team work patiently to expose more of the skeleton.

And, as they do so, the bones reveal something very intriguing.

♪♪ I've come down to Chris's workshop to take a look.

MOORE: It's a bit of a squeeze past the plesiosaur.

ATTENBOROUGH: It really is an Aladdin's cave.

After weeks of work, Chris has exposed the backbones and ribs.

-MOORE: So this is it so far. -ATTENBOROUGH: Gosh.

And, in doing so, he's made a startling discovery.

MOORE: It looks like it's been attacked. Gosh.

MOORE: There's breakages all through the rib cage.

If you follow one rib, you go along here, down to here, then this piece corresponds to this which then goes over to here, so... -ATTENBOROUGH: Oh, there, yeah. -MOORE: ...one rib is now broken into three pieces.

ATTENBOROUGH: How extraordinary.

But what's happened here?

MOORE: Here the vertebrae column has been actually pulled away.

I'm fairly positive it was done in life.

And the paddles, the flippers have been ripped off.

ATTENBOROUGH: Where would they go?

But they're in a very odd position, aren't they?

I mean, they're pointing in the wrong direction.

MOORE: They should be, basically, in this position and facing the other way up, and they've been ripped off and turned over.

ATTENBOROUGH: Gosh. Well, where was the head?

MOORE: The head should be here.

That's the very last vertebrae.

-ATTENBOROUGH: Back of the neck? -MOORE: Yeah.

So the head's been torn off and there's no evidence, there's no teeth or pieces of bone; it's completely gone.

ATTENBOROUGH: So it's a murder?

-MOORE: Yes. -ATTENBOROUGH: Really?

MOORE: Yeah, I think it was killed.

ATTENBOROUGH: Did this predator crunch the head, do you think?

MOORE: Who knows, you know?

It's 200 million years ago, so it's a bit of guess work, really, isn't it?

ATTENBOROUGH: So it's a murder story without a complete body yet?

To find out more, we need to reveal the rest of the skeleton.

♪♪ So it's all hands on deck.

♪♪ ♪♪ They've even roped me in.

♪♪ ♪♪ [Buzzing] This is more difficult than it looks.

MOORE: Very good.

Could you start on 3 days a week?

ATTENBOROUGH: [Laughs] Is it alright? -MOORE: It's good, yeah.

ATTENBOROUGH: I haven't gone too close to the bone.

MOORE: No, no.

ATTENBOROUGH: Phew, that's a relief.

But what of the missing head?

If it was been ripped off, Chris thinks he might still be able to find it somewhere on the beach.

So, at every opportunity he scours the area where the first block was found.

♪♪ The best time to look is after a storm when a strong sea has moved sand and shingle and perhaps revealed the rocks beneath.

♪♪ To try and deduce just how our Ichthyosaur met its fate, we've sent images of the fossil to someone who specializes in investigating the cause of death in pre-historic animals.

MARTILL: You sent me some photographs, and I had a look at some of these breaks.

First of all I noticed this here... if you look you can just see this bulbous piece on the rib here.

This is where the rib has healed after a break and the animal's gone on to live another day.

This animal's had a little bit of a bad start in life.

-MOORE: Yes. -MARTILL: If you look down here and especially this one if you look.

This fracture here mirrors that fracture there and then we can see a whole line of fractures where there's no new bone growth.

Something has actually crushed this rib cage.

So look here at these neural spines - these are absolutely perfect -- and then from here -- they're broken all the way down to here -- this is the last one that's broken and then here they're perfect again.

So there to there is damaged, on the ribs there to there is damaged and here, too, and also on some of these belly ribs.

So I think there's a bite which goes right across here.

That probably reflects the width of the skull of the animal that bit it.

MOORE: Yes. Yep, yeah.

Yeah so it came in across here almost... MARTILL: Somewhere like that yeah.

There was a massive bite; it caused catastrophic injury, and remember the rib cage is protecting lungs.

This was an air-breathing marine animal so once this rib cage is punctured, and the lungs are punctured, this animal is dead.

It can't breathe and also it's going to sink straight down to the seafloor as well.

It's quite likely that the animal that killed this animal, presumably it was looking for food -- it didn't get to eat it.

MOORE: Oh, no, I think it just killed it.

It didn't eat it or else it wouldn't be so intact.

MARTILL: So this probably all took place in the surface water.

But as soon as it had done this injury, this thing just sank like a stone straight down to the sea floor and then it was lost to the animal that was trying to eat it.

ATTENBOROUGH: So it looks as if Chris's attack theory might be right.

But what type of creature could possibly have inflicted so much damage to our sea dragon?

A rather unusual fossil in Chris's collection might give us a clue.

This is fossilized ichthyosaur droppings called a coprolite, and what makes it particularly interesting is that within this piece of dung, you can see fish scales.

So that shows that ichthyosaurs were fish eaters, but more than that... this one is even more interesting.

Because in this piece of dung are teeth, ichthyosaur teeth -- so the animal that produced this was almost certainly a cannibal.

It ate other ichthyosaur species.

Could it be that our dragon was killed by one of its own kind?

To find out more, I've come to the Natural History Museum of Stuttgart in Germany.

Here they have one of the most impressive and varied collections of ichthyosaurs in the world.

They came in all shapes and sizes.

But of all the ichthyosaurs that existed 200 million years ago there was one which was particularly fearsome.

This is Temnodontosaurus, one of the biggest of the sea dragons so far discovered.

They grew up to 10 meters long, and individual bones have been discovered which suggest that they could grow even bigger than that.

The remains of these terrifying sea monsters were discovered in a quarry just outside Stuttgart.

These are the biggest complete Temnodontosaurus fossils ever found.

This huge predator had the largest eye known of any animal which would have given it extremely acute eyesight.

Not only that, but the eye was surrounded by a ring of scutes -- bony plates -- to protect it from the water pressure at depth.

So, with eyes the size of footballs, this monster was able to hunt at all depths of the Jurassic ocean.

It also had rows of sharp teeth that would have allowed it to rip apart almost anything.

These teeth are shaped like blades.

Well-suited for cutting into flesh.

And here's another specimen of Temnodontosaurus that is proof positive that it really was a hunter.

Here is its stomach and inside its stomach you can see these tiny, little circular bones which are the backbones, the vertebrae, of a baby ichthyosaur.

So we now know that Temnodontosaurus could devour young ichthyosaurs, but would one have been capable of eating an adult ichthyosaur like ours?

Fossils of Temnodontosaurus have been found in other regions, including the Jurassic Coast.

So this monster could well be our prime suspect.

To build our case further, we're going to analyze another specimen of the same species that was found on the Jurassic Coast.

This is the skull of a Temnodontosaurus, and as you can see, it's huge.

This specimen was found by Mary Anning on the Dorset Coast in the 19th century, and we are hoping that we may be able to use it with the latest techniques to tell us just how powerful these great jaws could be.

So, for the first time ever, our team of scientists are going to attempt to calculate the bite strength of a Temnodontosaurus.

The first step is to scan the skull.

These scans will help the team to not only reconstruct the Temnodontosaurus' skull, but also work out the size of its jaw muscles.

They can then assess the power of this huge predator's bite, and see if it was strong enough to kill our ichthyosaur.

Temnodontosaurs are unusual in that they had huge sharp teeth for cutting through flesh.

But how did other ichthyosaurs catch their prey?

To get a clue I've come to see a modern day predator in action.

That is a gharial crocodile from Indonesia.

Its jaws, as you can see, are not wide and flat like an African crocodile but long and thin, and because of that shape there's very little resistance to the water so they can snatch fish, which they do very effectively.

They're very formidable animals indeed.

Ichthyosaurs must have fed in much the same way as that.

Their jaws were very similar to those of the gharial.

Simple studs to grip the prey.

No need to chew it, because the jaws at the back were quite big enough to enable the animal to swallow their prey whole.

Just as the gharial does.

So it's likely that our ichthyosaur had teeth and jaws specially adapted to catch small slippery fish and squid just like a gharial crocodile.

♪♪ Back in Lyme Regis, the work on the bones has taken a dramatic turn.

Chris has found that there is fossilized skin over nearly the whole skeleton.

MOORE: It seems to be virtually covering the whole thing.

ATTENBOROUGH: It's rare to find any sign whatever of skin on fossils, let alone so much of it.

Fiann Smithwick, an expert on fossilized skin, has come to take a sample back to his lab.

SMITHWICK: We can look and see if there's any evidence of the original pigment preserved in the skin.

MOORE: Oh, it's a lovely piece.

SMITHWICK: That's really good, that'll be perfect.

ATTENBOROUGH: Fiann hopes that this remarkably preserved sample might tell us what the skin looked like and even what color it was.

♪♪ At the University of Bristol, he places a tiny sample of the fossilized skin in a machine that coats its surface with minute particles of gold.

♪♪ ♪♪ They will reflect the rays of a scanning electron microscope.

It's astonishing that you can actually see the remains of skin on such an ancient fossil.

♪♪ But this microscope can also magnify its structure tens of thousands of times.

SMITHWICK: Here we have exceptional level of preservation of the skin of our ichthyosaur, despite being 200 million years old.

So the structures we're looking at here are around half a micrometer across.

And a micro meter is one millionth of a meter, and you see here these little granules and these are preserved melanosomes.

Now, melanosomes contain the pigment that you have in mammal hair, in bird feathers and reptile skin, and the abundance of them and the distribution of them can tell us about the overall color patterns of the animal.

So having a high abundance means you're likely to be darker and having a low abundance means you're likely to be lighter.

This area has come from the back.

There's a large abundance of these melanosomes, there's a lot of pigment here and when we look at samples that have come from the bottom of the animal we don't see this pigment in this level of abundance.

So it most likely had a much darker back than it did a belly and this conforms to a type of color pattern known as countershading in modern animals.

ATTENBOROUGH: You can see countershading in lots of sea animals today, great white sharks for example.

Both predators and prey are colored in this way.

It makes it more difficult to see both from above and below.

SMITHWICK: So this is the first time that we've actually seen evidence of a counter-shaded pattern in an ichthyosaur.

ATTENBOROUGH: So that really is a step forward in our knowledge of these creatures?

SMITHWICK: It is, and it can tell us a huge amount about the way the animal might have lived.

ATTENBOROUGH: Just by looking at that picture.

SMITHWICK: Just from looking at these melanosomes.

ATTENBOROUGH: Great.

Today, counter-shaded animals tend to live in open water where there's good visibility.

Ichthyosaurs also lived in the open seas, so being camouflaged in this way would have been very valuable to them.

The latest scientific research suggests that counter-shading might also protect against ultra violet light and even help to regulate body temperature.

As an air-breathing creature, our ichthyosaur would have had to spend much time near the surface, so counter-shading could have been a benefit for that reason as well.

There are, of course many marine reptiles still living in the oceans today.

Like turtles.

The biggest of them is the leatherback, whose ancestors in fact were around at the same time as the ichthyosaurs.

Today they come ashore to nest in many places, including the Caribbean.

This huge leatherback turtle is laying her eggs.

She's hauled her way up from the sea, and dug a hole, and now she's depositing about 100 of them.

She'll then fill in the hole and then work her way down, back to the sea.

It's clearly a very laborious process.

And that's the challenge facing all reptiles that live in the sea -- having to come onto land to lay eggs.

Ichthyosaurs were reptiles and they lived in the sea, but they were so well adapted to a life at sea that they gave birth to live young.

And that would have saved the sea dragons making the dangerous journey onto land.

There is remarkable evidence that ichthyosaurs gave birth to live young in the Stuttgart museum.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ And here is a truly extraordinary, beautiful, almost poignant fossil.

Proof positive that ichthyosaurs gave birth to live young.

Here is the baby just at the moment as it's leaving the birth canal.

It comes out tail first and as soon as it was freed, it would have risen to the surface to take its first breath, but something happened before that did and here is the proof.

Whatever it was, death must have been instant.

♪♪ So ichthyosaurs gave birth to live babies just as many sharks do today.

♪♪ ♪♪ ♪♪ ♪♪ After several weeks of research, the team at Bristol University have managed to reconstruct the skull of the Temnodontosaurus so that they can analyze the power of its jaws.

How do you assess the strength of this animal's bite?

RAYFIELD: Well the first thing that we need to know is the volume of muscle that could fit into the back of the skull.

So the muscles are attaching round here and there are also, there's a group of muscles that are attaching further forward here, and if we know how much muscle volume there is we can estimate how much force that muscle can generate.

ATTENBOROUGH: And what did you discover?

RAYFIELD: We found out that our upper estimate of bite force was around 30,000 Newtons, and to put that in a modern day context, that's twice as powerful as the largest saltwater crocodile that's been measured.

ATTENBOROUGH: Twice as powerful?

RAYFIELD: Yes.

ATTENBOROUGH: So that's enormous. Yeah.

RAYFIELD: Yes, it's a very powerful bite force.

ATTENBOROUGH: So, this must have been the animal with the most powerful bite of its time, must it?

RAYFIELD: Yes. That's absolutely right -- Of its time, it would have been.

Not only did it have a powerful bite, its jaw-closing muscles also attach quite close to the jaw joint.

Now normally in animals where that happens they have quite a fast, but less forceful bite, but the fact that this animal is actually so big means that it has a fast bite, but also by virtue of its sheer size it also has a powerful bite too.

So it basically has the best of both worlds.

ATTENBOROUGH: So this was the king of the Jurassic sea?

-RAYFIELD: Or queen... -ATTENBOROUGH: Sorry.

[Laughs] Yeah.

RAYFIELD: [Laughs] ATTENBOROUGH: So it seems very likely that temnodontosaurus was strong enough not only to kill our sea dragon, but to rip its head clean off.

It must have been a terrifying battle.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ Our investigations have given us a pretty good idea of how our sea dragon died.

But can the reconstruction work carried out at Bristol University tell us more about its life?

♪♪ All the blocks containing the fossil have now been scanned.

With those scans, the team were able to separate the individual bones and then put them back together to create a 3D image of the ichthyosaur's body before it was attacked.

♪♪ They've added a head based on estimates of other ichthyosaur species.

♪♪ That's magnificent.

MOON: This is the whole animal, and we estimate that it may have been up to round about 4 1/2 meters long.

ATTENBOROUGH: Is that bigger than most in their line?

MOON: Yes, this is certainly bigger than most of the ichthyosaurs that we see at Lyme Regis.

ATTENBOROUGH: Looks huge; looks amazing.

MOON: Here are the forelimbs, right at the front, and we've got hindlimbs here and, at the back, we've got a tail bend.

This is supported by the backbone, which extends along the whole length of the body.

ATTENBOROUGH: But that bend is natural, isn't it?

MOON: Yes.

ATTENBOROUGH: That's not a break.

That gives strength to the lower element of the tail for driving it forward. -MOON: Yes. Much like a shark.

The tail bend is the main propulsive organ of the animal.

ATTENBOROUGH: So could this be a new species?

MOON: Yes. These pieces of evidence together suggest that it is going to be a new species and it's jolly exciting.

They don't come along every day.

-ATTENBOROUGH: Historic. -MOON: Yes.

ATTENBOROUGH: This is wonderful news: a sighting by Chris on the beach in Lyme Regis has led to the discovery of a new species of ichthyosaur, adding to our knowledge of these fascinating creatures.

It's extraordinary how much you can discover from one single fossil.

Digital reconstruction has allowed us to rebuild this animal to reveal how it looked and how it moved.

We've discovered for the first time that this creature was counter-shaded, but that didn't stop it from being attacked.

By analyzing its bones we've been able to work out that its most likely attacker was the Temnodontosaurs -- the most ferocious predator of the seas at that time.

♪♪ It's been a fascinating journey of discovery.

But for me the real wonder is the bones themselves -- I can't wait to see what they look like when they're finally cleaned.

♪♪ ♪♪ ♪♪ After many months of painstaking and patient preparation, Chris and his team have finally completed their work on the fossil of our ancient sea dragon.

MOORE: Here it is finished.

ATTENBOROUGH: Wow.

It's -- it's really beautiful, isn't it?

I mean, it is beautiful, that's for sure.

MOORE: Thank you. It's a great specimen isn't it?

ATTENBOROUGH: Lovely.

And how many new species have been discovered in the last 100 years?

MOORE: Very few, very, very few, and it's thrilling to find something that's -- that's, you know, just never been seen before.

ATTENBOROUGH: Well, it's a long time spent just revealing the -- the body of this creature, but it's also revealed this extraordinary story of life and death, predator, prey, fighting it out in the seas 200 million years ago just down there in the bottom of the lane.

MOORE: Yeah. It's a fantastic story.

ATTENBOROUGH: Exciting.

Really, really thrilling and romantic.

For Chris, this has been a labor of love, and it's filled in another gap in the paleontological jigsaw, a story that all started with an odd-looking boulder on a Dorset beach.

It's extraordinary to think that some 200 million years ago, exactly here, the greatest predator of its time was swimming around in the sea.

And that's what I really love about fossils and fossil hunting.

It gives you an extraordinarily vivid insight into what the world was like millions of years before human beings even appeared on this planet.

♪♪ Ichthyosaurs died out around 90 million years ago.

No one knows why, but standing here, and having excavated that spectacular fossil it's not difficult to imagine a time when dragons really did rule the seas.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ [ Suspenseful music plays ] [ Grumble ] McCOMB: Horses are eavesdropping on the human world all the time.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪