1
00:00:51,567 --> 00:00:55,879
A fossil jaw, and little doubt
about the animal to which it once belonged
2
00:00:55,887 --> 00:01:00,722
because similar animals
with similar jaws are alive today.
3
00:01:06,607 --> 00:01:10,839
The delicate imprint of a dragonfly in limestone.
4
00:01:12,367 --> 00:01:14,676
It's so similar to a living dragonfly
5
00:01:14,767 --> 00:01:20,444
that it must have lived and flown
in just the same fashion 150 million years ago.
6
00:01:23,607 --> 00:01:27,202
A 50 million-year-old shell of a nautilus.
7
00:01:27,447 --> 00:01:30,519
We can be pretty sure
what kind of animal lived in it
8
00:01:30,807 --> 00:01:33,799
because nautilus still swim in the Pacific.
9
00:01:39,247 --> 00:01:42,523
But many fossils are much more mysterious.
10
00:01:42,607 --> 00:01:45,326
What could these bones have belonged to?
11
00:01:52,207 --> 00:01:54,516
Back at the beginning of the 18th century,
12
00:01:54,607 --> 00:01:59,681
a group of objects just like these
were found near Nuremberg in Germany.
13
00:01:59,887 --> 00:02:04,915
The man who discovered them was a doctor
and he thought he knew exactly what they were.
14
00:02:05,167 --> 00:02:08,159
They were, he said, part of a human backbone,
15
00:02:08,047 --> 00:02:13,724
the remains of a poor sinner
who had died at the time of the biblical flood.
16
00:02:13,807 --> 00:02:16,719
But, in fact, they're not shaped
like human vertebrae.
17
00:02:17,167 --> 00:02:23,481
However, a century later, this woman
found some more on the south coast of England.
18
00:02:23,687 --> 00:02:27,521
Her name was Mary Anning
and she earned her living at Lyme Regis
19
00:02:27,527 --> 00:02:30,121
by selling fossils to visitors.
20
00:02:30,407 --> 00:02:33,877
These new specimens of hers
were particularly interesting
21
00:02:33,767 --> 00:02:39,399
because with the backbones
were ribs and limbs and skulls.
22
00:02:39,527 --> 00:02:43,918
She sold one of them to a London surgeon
who was also a fossil collector.
23
00:02:44,327 --> 00:02:48,843
He thought at first that they were
some kind of fish. Then he changed his mind.
24
00:02:49,127 --> 00:02:54,247
He thought they were related,
believe it or not, to the duck-billed platypus.
25
00:02:54,407 --> 00:02:57,922
And finally he decided
that their nearest living relative
26
00:02:57,767 --> 00:03:03,444
was a strange creature that occasionally
appeared in the streams of Yugoslavia.
27
00:03:07,487 --> 00:03:14,165
This odd animal and others like it were
thought locally to be the tadpoles of dragons.
28
00:03:14,207 --> 00:03:18,246
In fact, it's an olm,
an amphibian related to salamanders.
29
00:03:18,527 --> 00:03:21,917
But even its bones don't match the fossil ones.
30
00:03:22,007 --> 00:03:26,637
Eventually, experts at the British Museum
got to the truth of the matter:
31
00:03:26,927 --> 00:03:32,684
There was nothing alive today
that was like the fossils of Lyme Regis.
32
00:03:32,687 --> 00:03:34,757
But the skull seemed very reptilian
33
00:03:35,087 --> 00:03:38,204
and the paddle-like limbs
showed that the animal swam.
34
00:03:37,967 --> 00:03:42,518
So they invented a special name for it,
ichthyosaur, "fish-lizard".
35
00:03:43,967 --> 00:03:49,644
As more specimens were found, they tried
to work out what the living animals looked like.
36
00:03:49,727 --> 00:03:52,036
The spine always had a kink at the end.
37
00:03:52,127 --> 00:03:55,278
That, they decided,
was because the fleshy tail was so big
38
00:03:55,487 --> 00:03:59,400
that when the animal died, it drooped and broke.
39
00:03:59,687 --> 00:04:03,726
The huge eye and the teeth suggested
that it was a hunter.
40
00:04:04,007 --> 00:04:08,285
Victorian illustrators
began to picture ichthyosaurs in life,
41
00:04:08,327 --> 00:04:11,125
and this is how they saw them.
42
00:04:20,327 --> 00:04:24,206
Then a lot more evidence came from Germany.
43
00:04:32,807 --> 00:04:35,082
In the village of Holzmaden, near Stuttgart,
44
00:04:35,607 --> 00:04:41,523
there are thick deposits of black, slaty limestone
of about the same age as the Lyme Regis rocks.
45
00:04:41,767 --> 00:04:44,600
Careful examination showed
that they were once mud
46
00:04:44,367 --> 00:04:48,121
on the floor of a wide bay in a tropical sea.
47
00:04:53,087 --> 00:04:58,036
Most of the inhabitants in this sea
swam in the sunlit upper waters,
48
00:04:58,367 --> 00:05:02,724
but the bay, it seems, was very tranquil
and undisturbed by currents.
49
00:05:03,647 --> 00:05:09,199
At the bottom, the water was still,
stagnant, and very poor in oxygen.
50
00:05:09,407 --> 00:05:11,398
Few scavengers could live down here
51
00:05:11,807 --> 00:05:16,562
and the processes of decay, which depend
on oxygen, could only move very slowly.
52
00:05:16,607 --> 00:05:20,725
So if the corpse of an animal
that had been living in the waters above
53
00:05:20,927 --> 00:05:23,646
slowly drifted down here,
54
00:05:23,807 --> 00:05:30,246
it could settle on the bottom and remain entire,
undecayed and undisturbed by scavengers,
55
00:05:30,047 --> 00:05:34,165
until mud settled down upon it and buried it.
56
00:05:34,367 --> 00:05:38,918
And here are the remains of just such a corpse.
57
00:05:49,447 --> 00:05:53,963
The tip of its snout
lies beyond this natural joint in the rock.
58
00:05:53,767 --> 00:05:59,160
These are its jaws, its eye is somewhere there,
its neck, its backbone,
59
00:05:59,527 --> 00:06:01,836
a few vertebrae are displaced here,
60
00:06:01,927 --> 00:06:07,524
then the backbone runs through this rock here,
past this imprint of an ammonite.
61
00:06:07,687 --> 00:06:10,759
There it is in this crack again, a backbone,
62
00:06:11,047 --> 00:06:15,040
and past another ammonite, and there's its tail.
63
00:06:15,847 --> 00:06:19,556
When such near-perfect specimens
are carefully prepared,
64
00:06:20,087 --> 00:06:22,885
they may even show the outline of the flesh,
65
00:06:22,967 --> 00:06:26,721
as a dark, almost oily
silhouette around the bones.
66
00:06:26,807 --> 00:06:32,803
And from this it was discovered that the
ichthyosaurs had a triangular fin on their back.
67
00:06:35,927 --> 00:06:39,761
And that kink at the end of the backbone
was not a break,
68
00:06:39,767 --> 00:06:43,282
but a strengthening of the lower fluke of the tail.
69
00:06:47,527 --> 00:06:54,000
With the whole shape of the animal revealed,
we can now work out just how it swam.
70
00:06:57,127 --> 00:07:00,278
The joints between the bones of its spine
showed that it beat its tail from side to side,
71
00:07:02,407 --> 00:07:04,762
and it was clearly capable of great speeds
72
00:07:04,807 --> 00:07:09,039
as it surged through the sea
in search of its food.
73
00:07:20,447 --> 00:07:25,237
No, not ichthyosaurs
but their modern equivalent, dolphins.
74
00:07:25,247 --> 00:07:27,044
There are, of course, differences.
75
00:07:27,167 --> 00:07:30,921
Dolphins beat their tails
not from side to side but up and down,
76
00:07:31,007 --> 00:07:33,316
and they are mammals, not reptiles.
77
00:07:33,407 --> 00:07:35,967
But their lifestyle is certainly very similar.
78
00:07:36,287 --> 00:07:38,755
Like ichthyosaurs, they breathe air...
79
00:07:41,087 --> 00:07:44,921
... and break the surface
every now and then to do so.
80
00:07:54,727 --> 00:07:59,960
After the ichthyosaurs died out, the seas,
for a time, had no air-breathing hunters.
81
00:08:00,047 --> 00:08:03,084
But then a group of mammals
began to colonise the sea,
82
00:08:03,407 --> 00:08:07,116
just as a group of reptiles had done
100 million years earlier,
83
00:08:06,887 --> 00:08:12,996
and similar ecological demands
have produced similar evolutionary responses.
84
00:08:17,327 --> 00:08:20,603
Did ichthyosaurs, like dolphins, eat fish?
85
00:08:20,687 --> 00:08:24,805
Well, their teeth were sharp and easily capable
of grabbing a wriggling fish,
86
00:08:25,647 --> 00:08:27,956
but they certainly ate other things as well.
87
00:08:28,047 --> 00:08:31,437
This one's belly contained
a number of small, horny hooks,
88
00:08:31,407 --> 00:08:35,161
and those, we know,
came from squid-like animals.
89
00:08:36,687 --> 00:08:38,518
But this is only one species.
90
00:08:38,567 --> 00:08:45,120
There are lots of different kinds of ichthyosaurs,
and each may have had its own particular diet.
91
00:08:46,247 --> 00:08:52,243
This one was a giant, four or five times
the length of the common ichthyosaur,
92
00:08:52,487 --> 00:08:54,557
and it was a cannibal,
93
00:08:54,887 --> 00:08:58,880
because here, between its ribs,
where its stomach once lay,
94
00:08:59,087 --> 00:09:03,763
are the chewed-up remains
of the backbones of smaller ichthyosaurs.
95
00:09:05,647 --> 00:09:12,280
And in addition to this monster, there was
another kind which is still something of a mystery.
96
00:09:21,447 --> 00:09:23,756
Its jaws are extraordinary.
97
00:09:23,887 --> 00:09:27,766
This is the upper one. It's a long, thin spike.
98
00:09:27,927 --> 00:09:33,320
The lower one is only a quarter of the length,
and it's fully armed with teeth.
99
00:09:33,207 --> 00:09:37,086
What could it have used them for?
Well, there are two clues.
100
00:09:37,407 --> 00:09:42,401
The first are its paddles,
which are huge and very broad.
101
00:09:42,687 --> 00:09:46,999
That suggests that
they could only be moved very slowly.
102
00:09:47,167 --> 00:09:50,637
Secondly, its eyes are gigantic.
103
00:09:50,527 --> 00:09:54,805
They're the biggest of all known ichthyosaur eyes.
104
00:09:55,327 --> 00:10:00,117
Big eyes are characteristic of animals
that live in low light levels.
105
00:10:00,127 --> 00:10:06,646
So maybe this, the rarest of the ichthyosaurs,
lived in the darkness near the bottom of the sea
106
00:10:06,847 --> 00:10:11,967
and moved across the sea floor,
propelling itself slowly with its huge paddles,
107
00:10:12,127 --> 00:10:15,597
stirring up the mud with its long upper jaw
108
00:10:15,487 --> 00:10:19,321
and snapping up
what food it found with its lower.
109
00:10:24,767 --> 00:10:27,440
The marvellously preserved
specimens of Holzmaden
110
00:10:27,647 --> 00:10:32,084
reveal a further detail
in the lives of these ancient reptiles.
111
00:10:32,447 --> 00:10:36,440
Just emerging from the body
of this female is a baby.
112
00:10:36,287 --> 00:10:38,642
Most reptiles lay eggs on land,
113
00:10:39,167 --> 00:10:45,037
but the ichthyosaurs had broken this last link
with the land and produced live young.
114
00:10:45,447 --> 00:10:47,915
Ichthyosaur or dolphin?
115
00:10:47,847 --> 00:10:54,286
150 million years ago, there must have been
events just like this in Holzmaden lagoon.
116
00:10:58,247 --> 00:11:01,557
While ichthyosaurs were swimming
so efficiently through the water,
117
00:11:01,607 --> 00:11:05,395
other animals were moving around
over the sand and mud of the sea floor.
118
00:11:05,527 --> 00:11:10,601
Some were even managing to crawl
out of the sea and up onto the land.
119
00:11:12,727 --> 00:11:16,481
And here they left
other evidence of their presence.
120
00:11:22,007 --> 00:11:24,760
A track can tell you a lot about an animal;
121
00:11:25,207 --> 00:11:31,237
how many legs it has, in what order it moved
them, how heavy it was and much else.
122
00:11:34,927 --> 00:11:39,523
And tracks, too,
can be preserved in sandstones.
123
00:11:40,287 --> 00:11:43,723
0n the shores of the Isle of Arran
in western Scotland,
124
00:11:44,127 --> 00:11:47,722
there are two parallel stripes in the rock.
125
00:11:53,207 --> 00:11:58,042
At first they might appear to be some kind
of stress mark or faulting in the stone,
126
00:11:58,487 --> 00:12:03,436
but look at them closely and you can see
that they are tracks of some kind.
127
00:12:03,287 --> 00:12:08,441
What is more, you can see that they were made
by an animal with a very large number of legs.
128
00:12:09,527 --> 00:12:12,803
There's an obvious candidate
for what made them;
129
00:12:15,767 --> 00:12:17,758
a millipede.
130
00:12:22,487 --> 00:12:27,083
Its multitude of legs, moving up and down
in a wave passing along the body,
131
00:12:27,287 --> 00:12:32,315
leave just such parallel stripes
in the mud behind it.
132
00:12:46,007 --> 00:12:50,125
They match these tracks in Arran almost exactly.
133
00:12:50,327 --> 00:12:57,165
The biggest millipede alive today is about ten
inches long, and we call that a giant millipede.
134
00:12:57,047 --> 00:13:00,403
But the animal that made these tracks,
judging from their dimension,
135
00:13:00,887 --> 00:13:03,526
must have been about six feet long.
136
00:13:03,287 --> 00:13:06,040
That was a real giant.
137
00:13:22,447 --> 00:13:27,999
Marks in sand and mud, of course,
can be made not only out of water but in it.
138
00:13:28,207 --> 00:13:30,926
And one of the commonest
of those underwater marks
139
00:13:31,087 --> 00:13:35,524
are the ones that are made when sand
is moved across the bottom of the sea
140
00:13:35,407 --> 00:13:38,877
as the tide moves in and out - ripple marks.
141
00:13:48,847 --> 00:13:55,082
These, too, are ripples in sand,
but they are 500 million years old.
142
00:13:55,087 --> 00:13:57,396
They were formed at the bottom of a sea
143
00:13:57,487 --> 00:14:01,196
which at that time covered
most of western Europe.
144
00:14:01,327 --> 00:14:07,721
Since then, continents have collided,
and those sediments have been rucked up
145
00:14:08,047 --> 00:14:13,883
so that now they form
these mountains in North Wales.
146
00:14:31,567 --> 00:14:37,278
It's not only inanimate mechanical forces that
create patterns in the sand of the sea floor,
147
00:14:37,327 --> 00:14:39,363
animals do so as well.
148
00:14:39,727 --> 00:14:43,003
They burrow through the sediment,
extracting nutriment from it,
149
00:14:43,087 --> 00:14:46,204
and they usually do so in a regular,
systematic way,
150
00:14:46,447 --> 00:14:51,043
so that they don't miss patches of mud
and don't process any of it twice,
151
00:14:51,247 --> 00:14:56,002
and this produces regular patterns
of casts and burrows.
152
00:15:03,247 --> 00:15:05,397
But many of these patterns are complicated,
153
00:15:05,647 --> 00:15:09,720
and it's not always easy to see
exactly how the animal could have made them.
154
00:15:09,967 --> 00:15:13,755
However, computers can help
to solve this problem.
155
00:15:14,127 --> 00:15:17,085
This is not a pattern
that has been generated by the computer.
156
00:15:17,007 --> 00:15:21,205
This is the tracing of an actual fossil,
but it's rather puzzling.
157
00:15:21,327 --> 00:15:23,602
Look, for example, at down here.
158
00:15:24,007 --> 00:15:30,924
There's one ring there,
but there is another ring on the inside.
159
00:15:31,287 --> 00:15:33,278
How could that have been formed?
160
00:15:33,207 --> 00:15:35,596
Well, by looking at the actual fossil itself,
161
00:15:36,087 --> 00:15:42,401
you can see which ring, which track
has been placed on top of which other track.
162
00:15:42,327 --> 00:15:46,081
And by feeding that information
carefully into the computer,
163
00:15:46,167 --> 00:15:50,797
you can then ask the computer to look
at the pattern from a different point of view,
164
00:15:50,967 --> 00:15:53,765
and then what you see is this.
165
00:15:58,567 --> 00:16:04,119
The animal was working in three dimensions,
it was burrowing down in the mud,
166
00:16:03,927 --> 00:16:08,717
and it was when the rock was compacted
that it produced this ring
167
00:16:09,207 --> 00:16:13,120
superimposed upon one another
and that particular shape.
168
00:16:14,487 --> 00:16:18,241
But although we know so much
about this elegant burrow,
169
00:16:18,207 --> 00:16:23,406
we don't know what animal made it
and may, in fact, never find out.
170
00:16:25,167 --> 00:16:27,476
These rocks in North Wales,
171
00:16:28,047 --> 00:16:32,518
close by those ancient,
500 million-year-old ripple marks,
172
00:16:32,367 --> 00:16:36,201
are also covered with trails of many kinds.
173
00:16:36,687 --> 00:16:39,326
One sort is like this.
174
00:16:39,087 --> 00:16:43,922
They are long tracks
which often criss-cross one another.
175
00:16:44,367 --> 00:16:49,760
And this is another kind, a sort of large dimple.
176
00:16:49,647 --> 00:16:51,638
What could have made them?
177
00:16:52,047 --> 00:16:57,075
Well, we have direct evidence
as to what made this kind.
178
00:16:57,327 --> 00:17:01,764
A fossil has been found that sits in it perfectly.
179
00:17:02,127 --> 00:17:07,679
A trilobite, the most abundant
of all the animals in the seas of this period.
180
00:17:13,647 --> 00:17:16,559
The dimple is where it rested,
181
00:17:16,527 --> 00:17:21,043
the broad stripe the track it made
as it trundled over the sea floor.
182
00:17:29,527 --> 00:17:35,045
Trilobites have left no direct descendants,
but we nevertheless know a lot about them.
183
00:17:34,807 --> 00:17:36,843
Underneath their hard, jointed shells
184
00:17:37,207 --> 00:17:40,995
they had two rows of long,
thin legs, as shrimps have.
185
00:17:41,367 --> 00:17:47,920
Most trilobites were only an inch or so long,
but a few were giants, over a foot in length.
186
00:17:52,407 --> 00:17:55,524
Although their remains all accumulated
on the bottom of the sea,
187
00:17:55,887 --> 00:17:58,196
they didn't necessarily all live there.
188
00:17:58,287 --> 00:18:00,278
Some may have grubbed about on the bottom,
189
00:18:00,687 --> 00:18:03,759
but others could have swum
quite a long way above the sea floor.
190
00:18:04,527 --> 00:18:08,998
To find out which did what,
casts are put in a tank of flowing water
191
00:18:09,287 --> 00:18:11,482
by Richard Fortey of the British Museum.
192
00:18:11,687 --> 00:18:14,247
What kind of animal is this one?
193
00:18:14,367 --> 00:18:20,840
This is a typical bottom-living trilobite,
which we think was rather poorly streamlined.
194
00:18:21,087 --> 00:18:26,081
And we can show this quite graphically
by turning on some dye.
195
00:18:28,767 --> 00:18:30,086
There it goes.
196
00:18:30,207 --> 00:18:34,200
And you can see that large wakes
are created on the back of the animal,
197
00:18:34,527 --> 00:18:37,758
behind the eyes and behind the tail.
198
00:18:42,127 --> 00:18:48,077
And if we turn the dye off, you can see how
these wakes linger on for a long time,
199
00:18:47,887 --> 00:18:50,560
behind the eyes and on the back of the animal.
200
00:18:50,767 --> 00:18:53,679
This is generally
a bad design for active swimming,
201
00:18:54,127 --> 00:18:59,759
as we might expect of an animal that spent
most of its time crawling along the sea floor.
202
00:19:04,687 --> 00:19:10,557
If we look at this one, by contrast,
you can see how well streamlined the animal is.
203
00:19:11,887 --> 00:19:16,165
The dye proceeds over the back of the animal
without the eddies we saw last time
204
00:19:16,207 --> 00:19:20,917
and the head of the animal, this end here,
is prolonged into a kind of nose,
205
00:19:21,007 --> 00:19:24,556
and the eyes are recessed,
it's almost like a dogfish head.
206
00:19:24,847 --> 00:19:29,398
So that is proof, do you think,
that this animal was free-swimming?
207
00:19:29,647 --> 00:19:32,115
I don't think we can ever talk about proof,
208
00:19:32,527 --> 00:19:37,237
but as far as we can test by experiment
and looking at the shape of the animal,
209
00:19:37,327 --> 00:19:42,321
this was a free-swimming trilobite
in the seas of 500 million years ago.
210
00:19:47,407 --> 00:19:52,925
It's clear from such investigations that
some trilobites, at any rate, were very active.
211
00:19:58,447 --> 00:20:02,599
Active animals need good sense organs
in order to find their way about,
212
00:20:02,767 --> 00:20:05,122
and trilobites had amazing eyes,
213
00:20:05,247 --> 00:20:09,206
the first complex eyes
ever to gaze out on this world.
214
00:20:09,087 --> 00:20:12,841
Each consisted of a mosaic of tiny,
tightly-packed units,
215
00:20:12,927 --> 00:20:18,877
which produced separate spots of light or
shade, and together formed a single picture.
216
00:20:19,167 --> 00:20:22,716
Crabs have very much
the same sort of eye today.
217
00:20:25,647 --> 00:20:27,922
But some trilobites did even better.
218
00:20:28,047 --> 00:20:33,724
Each element in their eye had a little lens over it
which focused the light into a separate image.
219
00:20:33,807 --> 00:20:37,004
This intricate structure
was mounted on a kind of turret.
220
00:20:37,247 --> 00:20:40,398
A pair of these on the head
gave this trilobite a view
221
00:20:40,607 --> 00:20:44,316
that extended from its tail
right round to its nose.
222
00:20:44,447 --> 00:20:48,326
But why should it have needed
such a detailed view of its surroundings?
223
00:20:48,287 --> 00:20:51,563
Well, there were hunters in those ancient seas.
224
00:20:51,647 --> 00:20:55,083
Ancestors of cuttlefish were around,
stalking trilobites,
225
00:20:55,327 --> 00:20:59,525
just as cuttlefish today hunt crabs.
226
00:21:15,807 --> 00:21:19,846
Once the trilobites were alarmed,
they had very good defences.
227
00:21:26,287 --> 00:21:29,518
You find them preserved
in many different postures.
228
00:21:29,647 --> 00:21:31,877
From specimens like these, it's evident
229
00:21:32,047 --> 00:21:36,006
that those joints between the segments
along the back were very flexible.
230
00:21:36,367 --> 00:21:42,602
When danger threatened, they were able to
protect their vulnerable undersides by rolling up.
231
00:21:45,967 --> 00:21:49,642
They even had little knobs on their heads
and sockets on their tails
232
00:21:49,807 --> 00:21:53,402
that enabled them to lock themselves into a ball.
233
00:21:59,487 --> 00:22:02,684
They evolved
into many thousand different species
234
00:22:02,847 --> 00:22:08,683
and then, 250 million years ago,
they died out and left no descendants.
235
00:22:08,607 --> 00:22:14,204
Yet from their remains we can still discover
how they moved and protected themselves,
236
00:22:14,367 --> 00:22:20,283
what they ate, where they swam,
even what they saw of that long-lost world.
237
00:22:24,167 --> 00:22:27,682
The skies above the ancient seas
were not empty either.
238
00:22:28,007 --> 00:22:30,362
Today it's birds that fly over the ocean,
239
00:22:30,407 --> 00:22:33,843
scouring the surface
for food of one kind or another.
240
00:22:34,247 --> 00:22:37,239
But birds are relatively recent arrivals.
241
00:22:37,127 --> 00:22:43,316
Millions of years before they appeared,
the air had been invaded by flying reptiles.
242
00:22:45,687 --> 00:22:49,566
The first to be discovered
was named "wing-finger", pterodactyl,
243
00:22:49,527 --> 00:22:53,600
for its wing was supported
by its greatly elongated fourth finger.
244
00:22:53,847 --> 00:22:56,077
Now so many different kinds have been found
245
00:22:56,247 --> 00:23:00,445
that the group as a whole is called
"winged reptiles" - pterosaurs.
246
00:23:00,567 --> 00:23:02,558
Their slim jaws are lined with teeth
247
00:23:02,967 --> 00:23:08,246
and they had a skinny membrane that stretched
from that long finger to the side of their body.
248
00:23:08,327 --> 00:23:12,718
This wing was powered by muscles
attached to the breastbone.
249
00:23:12,647 --> 00:23:17,004
The fact that this is of a reasonable size
and had a small keel down the middle
250
00:23:17,447 --> 00:23:22,282
shows that the pterosaurs
were able to flap and not just glide.
251
00:23:23,447 --> 00:23:26,837
But we have more than just bones of pterosaurs.
252
00:23:26,807 --> 00:23:31,164
This is a very remarkable skull
of one that was found in the north of England.
253
00:23:31,487 --> 00:23:35,116
The front part of the snout is missing,
and so is the lower jaw,
254
00:23:35,327 --> 00:23:39,525
but here is the huge orbit
where the eye once was.
255
00:23:39,647 --> 00:23:45,597
And at the back, the top of the skull is missing
and you can see inside.
256
00:23:45,527 --> 00:23:49,202
At some stage during fossilisation,
sediment seeped in,
257
00:23:49,607 --> 00:23:53,680
and it's left a cast of the pterosaur's brain.
258
00:23:57,727 --> 00:24:01,402
Brains can tell us a great deal
about an animal's behaviour.
259
00:24:01,567 --> 00:24:04,684
And this is not the only pterosaur brain we have.
260
00:24:04,447 --> 00:24:10,079
One, separated from the skull
and marvellously preserved, was found in Israel.
261
00:24:10,687 --> 00:24:13,679
The lobes at the back of all brains
coordinate the muscles,
262
00:24:13,567 --> 00:24:16,604
and those at the front
link the muscles with the senses.
263
00:24:16,927 --> 00:24:22,001
All these lobes are much bigger
than in a similar-sized land-living reptile,
264
00:24:22,207 --> 00:24:25,517
which confirms that this animal
had the speedy reactions necessary
265
00:24:25,567 --> 00:24:28,001
for manoeuvrability in the air.
266
00:24:30,367 --> 00:24:34,360
The lobes at the side of the brain
control vision and are also large,
267
00:24:34,207 --> 00:24:38,564
so the pterosaurs had excellent sight
and probably flew during the day.
268
00:24:43,007 --> 00:24:45,202
With their skinny wings and short feet,
269
00:24:45,207 --> 00:24:48,199
the pterosaurs may have looked
more like bats than birds.
270
00:24:48,647 --> 00:24:51,844
There's another way in which
they may have resembled them.
271
00:24:52,087 --> 00:24:54,840
Flying like this demands a lot of energy.
272
00:24:55,007 --> 00:24:58,795
Bats can produce it because
they have warm bodies insulated with fur.
273
00:24:58,727 --> 00:25:02,879
What about pterosaurs?
Could reptiles have warm blood?
274
00:25:03,047 --> 00:25:06,881
And if they did, how did they keep it warm?
275
00:25:09,007 --> 00:25:13,558
These remarkable pterosaur fossils
from Kazakhstan in the Soviet Union
276
00:25:13,807 --> 00:25:16,002
provide an answer to that question.
277
00:25:16,207 --> 00:25:20,519
Around the body of this one
is the unmistakable imprint of fur,
278
00:25:20,527 --> 00:25:24,884
and what is fur for
if it's not to keep a body warm?
279
00:25:33,727 --> 00:25:37,686
The pterosaurs first appeared
245 million years ago,
280
00:25:37,607 --> 00:25:41,998
and they populated the skies
for the next 170 million years.
281
00:25:42,207 --> 00:25:45,802
The earliest ones were about the size
of sparrows and had bony tails,
282
00:25:46,447 --> 00:25:49,962
but, as time passed, they got bigger and bigger.
283
00:25:56,407 --> 00:26:00,400
Judging from their teeth,
they had a wide variety of diets.
284
00:26:00,727 --> 00:26:06,120
Some of the smaller ones, with well-spaced,
simple teeth like this, may have fed on insects,
285
00:26:07,367 --> 00:26:11,565
but this one, from the rocks of Bavaria,
is very different.
286
00:26:11,687 --> 00:26:15,885
Its teeth are so long and thin
that they're little more than bristles.
287
00:26:16,367 --> 00:26:20,997
Did it use them to filter food
from the water, as a flamingo does?
288
00:26:23,927 --> 00:26:27,556
Nearly a hundred different kinds
have been found already,
289
00:26:27,767 --> 00:26:31,999
and there are undoubtedly
a great number still to be discovered.
290
00:26:32,167 --> 00:26:36,160
One of the most productive areas
in recent years has been Brazil.
291
00:26:36,487 --> 00:26:40,366
Some extremely bizarre forms
have come from there,
292
00:26:40,327 --> 00:26:42,318
like this one.
293
00:26:43,687 --> 00:26:47,760
It's very big, the skull alone is over two feet long,
294
00:26:48,007 --> 00:26:53,365
and at the end of its upper jaw
there is this extraordinary flange.
295
00:26:55,727 --> 00:27:00,562
Peter Wellnhofer, a pterosaur expert
working in Munich University,
296
00:27:01,007 --> 00:27:03,680
has been investigating these new finds,
297
00:27:03,647 --> 00:27:08,641
trying to work out what possible purpose
such extraordinary features could have.
298
00:27:09,007 --> 00:27:14,639
It cannot be an aerodynamic stabiliser.
299
00:27:14,767 --> 00:27:20,364
It probably would not make much sense
on the very end of the snout.
300
00:27:20,527 --> 00:27:24,918
So no use in flying.
They can't use it to steer with or anything.
301
00:27:24,847 --> 00:27:31,082
But probably it had a function
when it was diving and skimming in the water,
302
00:27:31,567 --> 00:27:38,484
and during that time it was necessary to stabilise
this long and narrow skull in the water.
303
00:27:38,607 --> 00:27:42,964
As you can see here in this restoration,
304
00:27:42,927 --> 00:27:47,398
the skull must bend back when it dives down,
305
00:27:47,727 --> 00:27:54,326
but it still flies and it's moving through the water
and it has to come up again.
306
00:27:57,527 --> 00:28:02,123
Frigate birds pick up food from the water
with just this sort of action.
307
00:28:02,327 --> 00:28:06,684
The pterosaur's membranous wings probably
gave it less control than feathered wings,
308
00:28:06,927 --> 00:28:10,840
so maybe a flange on the beak
was essential for the pterosaur
309
00:28:11,007 --> 00:28:13,601
if it was going to do this trick.
310
00:28:16,367 --> 00:28:21,202
I asked Peter Wellnhofer how he reconstructed
the appearance of these pterosaurs.
311
00:28:21,367 --> 00:28:25,679
This requires some degree
of imagination, of course.
312
00:28:25,807 --> 00:28:32,121
0n the other hand, we know that pterosaurs,
for example, had hairs.
313
00:28:32,047 --> 00:28:38,919
And so we put hair on the skull
in the restorations, as you can see here.
314
00:28:39,447 --> 00:28:46,080
And so you get a fairly good picture
of what the animal looked like in life.
315
00:28:47,607 --> 00:28:52,237
And what an extraordinary
portrait gallery he has produced.
316
00:28:59,127 --> 00:29:04,201
This is one of the filter feeders,
with bristles on its lower jaw only.
317
00:29:06,207 --> 00:29:10,758
This one, pteranodon,
like many of the later kinds, had no tail,
318
00:29:11,007 --> 00:29:13,601
but its wings were 18 feet across.
319
00:29:13,887 --> 00:29:18,358
Its wing muscles, judging from its breastbone,
were not particularly powerful,
320
00:29:18,687 --> 00:29:21,963
so that it's likely that it was primarily a glider.
321
00:29:21,727 --> 00:29:25,879
But you can get a long way gliding over the sea.
322
00:29:32,767 --> 00:29:34,439
Pelicans show what can be done
323
00:29:34,687 --> 00:29:39,807
if you are able to exploit
the updraughts created by the rolling waves.
324
00:29:58,367 --> 00:30:03,157
And pteranodon was probably just as expert.
325
00:30:15,127 --> 00:30:19,439
But perhaps the most extraordinary,
indeed almost unbelievable pterosaur
326
00:30:19,447 --> 00:30:22,678
was found here in the badlands
of southern Texas.
327
00:30:22,807 --> 00:30:27,164
In 1971, a group of students
working with Professor Wann Langston
328
00:30:27,607 --> 00:30:30,041
were down here looking for dinosaur bones
329
00:30:30,007 --> 00:30:34,080
when one of them, Douglas Lawson,
found something very strange.
330
00:30:35,287 --> 00:30:41,123
Late one hot July afternoon,
after he had spent an almost fruitless day,
331
00:30:41,447 --> 00:30:44,484
he was walking up this dry arroyo
332
00:30:44,327 --> 00:30:51,324
and began to see postage stamp-sized fragments
of petrified bone down in the sand.
333
00:30:52,007 --> 00:30:55,317
And as he followed on up the valley,
334
00:30:55,367 --> 00:30:59,201
the fragments became more numerous and larger,
335
00:30:59,487 --> 00:31:06,484
and eventually he arrived over here at this bank
336
00:31:06,687 --> 00:31:12,364
and there he found a few pieces of bone
projecting from the rock, still in place,
337
00:31:12,447 --> 00:31:18,556
and other, larger pieces that had weathered out
were lying around on the surface.
338
00:31:19,847 --> 00:31:25,956
This is a replica
of the upper arm-bone in the wing.
339
00:31:26,087 --> 00:31:31,764
As it turned out, this was the only piece that was
nearly complete and still embedded in the rock,
340
00:31:31,847 --> 00:31:34,725
but it gives an idea of the size of the wing
341
00:31:35,207 --> 00:31:38,119
and taken together
with all the fragments that were picked up,
342
00:31:38,087 --> 00:31:41,397
we've been able to piece together
a reconstruction of the entire wing.
343
00:31:41,447 --> 00:31:43,836
I just happen to have a diagram here
344
00:31:44,327 --> 00:31:48,400
that will give us some idea
345
00:31:48,567 --> 00:31:52,685
about the size of this object.
346
00:32:05,367 --> 00:32:09,679
So this is the reconstruction of the entire wing.
347
00:32:09,687 --> 00:32:14,841
The dark areas represent the pieces
that we actually have found as fossils.
348
00:32:14,967 --> 00:32:20,087
And from the shoulder joint out to this tip
is a length of about 18 feet.
349
00:32:20,247 --> 00:32:22,238
And remember this is only one wing,
350
00:32:22,647 --> 00:32:27,437
so you double the 18 feet and add
a couple of feet for the body in between
351
00:32:27,447 --> 00:32:32,077
and you come up with an animal
that had a wingspan of maybe 35 to 40 feet,
352
00:32:32,447 --> 00:32:36,884
which is larger than some small private aircraft.
353
00:32:42,007 --> 00:32:44,726
How could such a huge creature have flown?
354
00:32:45,127 --> 00:32:48,324
Wann Langston studied the bones of a smaller
individual of the same species in his laboratory
355
00:32:49,927 --> 00:32:51,724
to try and find out,
356
00:32:51,847 --> 00:32:56,045
suspending them in position to see just
how they could move and how they couldn't.
357
00:32:56,647 --> 00:32:59,320
We can take the humerus
358
00:32:59,047 --> 00:33:05,441
and because of the configuration of the head,
fitting into the shoulder socket,
359
00:33:05,767 --> 00:33:10,158
we can move the humerus
up to its maximum possible elevation.
360
00:33:10,567 --> 00:33:15,357
We can also depress it to the limit
361
00:33:15,367 --> 00:33:21,237
and we can move it backward and forward in
this plane, which also was possible for the animal.
362
00:33:21,607 --> 00:33:28,001
And every move that we make with the humerus
has an effect, of course, on the rest of the wing.
363
00:33:29,007 --> 00:33:32,966
With all this detailed information
about the mechanics of the wing available,
364
00:33:33,327 --> 00:33:37,764
the Smithsonian Institution in the United States
decided to commission a model of one
365
00:33:37,927 --> 00:33:41,124
that would actually flap its wings and fly.
366
00:33:41,367 --> 00:33:45,440
The cost of making one with a 40-foot wingspan
would have been astronomic,
367
00:33:45,687 --> 00:33:50,807
so they decided to make a half-grown one,
but even that is immense.
368
00:33:50,847 --> 00:33:55,716
It was built from carbon-fibre materials
which are very light and extremely strong.
369
00:33:55,687 --> 00:33:58,440
It was coated with foam
and then covered with latex,
370
00:33:58,567 --> 00:34:03,118
which is very flexible and allows the wing
to make all the necessary movements.
371
00:34:05,647 --> 00:34:10,846
The man who took on this job is aeronautical
engineer and inventor Paul Macready.
372
00:34:10,927 --> 00:34:15,398
What was your reaction
when you first saw the fossils
373
00:34:15,247 --> 00:34:19,081
and the reconstructions made
by palaeontologists of a thing like this?
374
00:34:19,567 --> 00:34:23,640
Did it seem that it could possibly fly,
to you as an aeronautical engineer?
375
00:34:23,887 --> 00:34:28,039
Well, we knew it did fly,
but it didn't seem possible
376
00:34:28,207 --> 00:34:32,200
because it was reputed
to have a wingspan of 35 to 50 feet
377
00:34:32,047 --> 00:34:34,607
and that's so beyond anything that exists now
378
00:34:34,927 --> 00:34:38,681
that it almost seemed impossible,
but you knew nature had done it.
379
00:34:38,767 --> 00:34:44,763
So you, when you had to try and make
something of the same shape that flew,
380
00:34:45,007 --> 00:34:47,316
what were your immediate problems?
381
00:34:47,407 --> 00:34:49,875
First you had to figure out what the shape was.
382
00:34:50,287 --> 00:34:53,359
You pleaded with the palaeontologists,
"Tell us what it looked like."
383
00:34:53,447 --> 00:34:58,521
The main thing was a big head
stuck way out in front of a long neck
384
00:34:58,727 --> 00:35:00,797
and no tail to provide stability.
385
00:35:00,647 --> 00:35:02,239
Trying to have this fly
386
00:35:02,567 --> 00:35:06,958
is like trying to shoot an arrow
with the feathered end in front. It's very unstable.
387
00:35:07,007 --> 00:35:12,320
The earliest pterosaurs, little ones,
had tails in the rear and they were stable,
388
00:35:12,767 --> 00:35:16,077
but it's kinda like riding a bicycle
with training wheels.
389
00:35:16,127 --> 00:35:19,403
When it's small and you're early
in your training, you need that.
390
00:35:19,487 --> 00:35:22,797
When nature got to these,
it didn't need training wheels any more.
391
00:35:23,127 --> 00:35:24,845
Everybody ready?
392
00:35:27,887 --> 00:35:33,405
The first experiments were with small models,
fitted with tails to give them some stability
393
00:35:33,887 --> 00:35:38,199
while the designers wrestled
with the basic aerodynamic problems.
394
00:35:38,447 --> 00:35:41,484
Radio controls enabled them
to move the head and wings.
395
00:35:54,047 --> 00:35:58,677
With each flight, and each crash,
a new lesson was learnt.
396
00:36:04,007 --> 00:36:07,363
The damage caused by these crash-landings
was often severe,
397
00:36:07,447 --> 00:36:11,156
but slowly the engineers
were able to improve their design.
398
00:36:11,367 --> 00:36:15,076
Even with the aid of computers
and advanced aeronautical skills,
399
00:36:15,167 --> 00:36:20,480
this particular problem was so tricky
that much of the progress was by trial and error.
400
00:36:22,167 --> 00:36:24,761
After months of work, a half-sized,
401
00:36:25,087 --> 00:36:28,762
tailless, wing-flapping pterosaur
was ready to take to the air.
402
00:36:28,927 --> 00:36:32,442
Power on. Motion check.
403
00:36:33,007 --> 00:36:34,838
Left, right.
404
00:36:38,287 --> 00:36:40,596
Forward, aft.
405
00:36:40,727 --> 00:36:44,083
Take up the slack.
406
00:36:44,087 --> 00:36:46,123
Clear. Go.
407
00:37:01,247 --> 00:37:07,595
Once airborne, the tail and the undercarriage
needed for take-off are shed.
408
00:37:08,687 --> 00:37:10,996
Although major movements
are controlled by radio,
409
00:37:11,167 --> 00:37:14,637
the model controls itself
to a considerable degree.
410
00:37:14,527 --> 00:37:17,678
Sensors in the wings
react to the varying wind currents
411
00:37:17,887 --> 00:37:21,596
and automatically feed signals
to a small computer, a brain,
412
00:37:21,767 --> 00:37:26,238
which then activates tiny motors
to adjust the posture of the head and wings,
413
00:37:26,607 --> 00:37:30,600
so preventing stalls and sideslips.
414
00:37:36,127 --> 00:37:40,757
The last time such a shape flapped its way
across the skies of North America,
415
00:37:41,287 --> 00:37:44,438
the animals watching it were dinosaurs.
416
00:37:44,647 --> 00:37:51,120
You could hardly go farther than this
in bringing long-dead bones back to life.