Attenborough and the Sea Dragon Page #4

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We can actually start using

this paddle to try and tell us

what species it might have 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 ichthyosaurus

and so this could be a new species.

- That would be great.

- It would be jolly exciting.

VOICEOVER:
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?

There are a lot of bones in this paddle,

which would have been

good for holding steady

and also for allowing it to

be manoeuvrable in the water.

- There would have been cartilage

round that, wouldn't there? - Yes.

All of the gaps between the bones

would have 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 aerofoil

so that it could cut

straight through the water.

- Could they fold them in to the side?

- 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.

The shape of the paddles

and the way they moved

seems very like the way an animal

alive today uses its paddles.

That animal usually lives

in tropical waters

like these in the Caribbean.

The sea here is warm

with temperatures much

like they would have been

in Jurassic times around Britain.

And the animal in question...

is the dolphin.

Dolphins, of course, are mammals,

not reptiles like ichthyosaurs.

Nonetheless, the two groups have

bodies shaped in very similar ways.

The front fins or paddles of both

would have helped to steady themselves

as they turn and cut through the water.

And both have similar dorsal fins.

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

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 have swum

in the same sort of way

by sweeping their tails from side to side.

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