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Documentary, PaleoWorld PaeoWord S01E03 - Flight Of The Pterosaurs
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AnimalsTranscript
00:01The world's first great flyers were not birds.
00:05They took to the skies 60 million years before the first known bird.
00:09And then they vanished, leaving scant clues about how they lived.
00:13These were the pterosaurs, also known as the pterodactyls.
00:17These flying reptiles were cousins of the dinosaurs.
00:2465 million years after the last pterosaur disappeared, scientists ask,
00:30how did reptiles learn to fly?
01:09On the shores of the Niobrara sea, 85 million years ago, a young pterosaur stretches its wings for its first
01:17flight.
01:27With a wingspan of nearly 20 feet, it scans for its first prey beneath the blue waters.
01:39In the still waters of the Niobrara sea, carcasses drifted to the bottom and were fossilized, undisturbed by currents.
01:54Today, all that remains of the Niobrara sea is a dusty limestone chalk bed that runs from North Dakota to
02:01New Mexico.
02:03It is one of the few places in America where the fossils of pterodactyls are found.
02:08Like the dinosaurs, pterodactyls were reptiles, more akin to lizards than birds.
02:18Yet like birds, pterodactyls could fly.
02:24Among the last of these flying reptiles was pteranodon.
02:29Paleontologist Chris Bennett has spent thousands of hours prospecting for pterosaur fossils in the Niobrara chalk beds in western Kansas.
02:3885 million years ago, this would have been at the bottom of a sea.
02:42It would be about 200 meters deep.
02:45And it ran from the Arctic Ocean down to the Gulf of Mexico.
02:49And the near shore was about 200 kilometers from here.
02:54The sea would be full of large mosasaurs, seagoing glizzards, turtles, plesiosaurs, all sorts of fish.
03:03And above would be flying pteranodon.
03:06A typical day in the life of pteranodon would be flying out over this Niobrara seaway,
03:11soaring on the wind, flapping occasionally in order to gain altitude and so forth,
03:17but mostly soaring on the wind just as a lot of modern seabirds and large birds do today.
03:23They'd be chasing after schools of fish to feed and probably would be spending most of their time feeding.
03:29At night, they probably would just rest on the surface of the sea as living albatrosses do today.
03:35Over the past 125 years, 1,100 fossils of pteranodon have been unearthed here.
03:45In the autumn of 1870, the area was explored by eminent Yale paleontologist O.C. Marsh and his Wild West
03:52-style hunting party,
03:54toting guns and bowie knives.
03:56In the pioneer days of paleontology, the photos made good souvenirs to send to the folks back east.
04:02So, too, did the fossils of pteranodon.
04:07Marsh's discovery of pteranodon opened a new chapter in the history of pterosaurs.
04:13Pterosaurs were not dinosaurs.
04:15As far as paleontologists can determine, pterosaurs descended from small, lightweight, four-legged reptiles
04:22that lived about 250 million years ago.
04:25By 225 million years ago, the pterosaurs were accomplished flyers.
04:31The pterosaurs came in two evolutionary waves.
04:34The first of them were called rhamphorhynchoids, meaning pointy, curved nose.
04:41Their fossils revealed they were only about the size of pigeons.
04:45The rhamphorhynchoids had long, skinny heads filled with teeth probably used for plucking fish out of the water.
04:55These early pterosaurs had long, stabilizing tails, like the tail on a kite.
05:00Their definitive evolutionary feature was a super pinky.
05:04The fourth finger on each hand had become longer than their entire bodies and supported a wing.
05:10The other fingers, normal-sized, developed claws.
05:15The first rhamphorhynchoids date back more than 200 million years.
05:19By 150 million years ago, they had evolved in great variety and covered the globe.
05:26The fossil record of the rhamphorhynchoids spans almost 50 million years, from 230 to 180 million years ago.
05:34For unknown reasons, by 180 million years ago, the rhamphorhynchoids vanished.
05:38A second stage of pterosaur, the pterodactyloids rushed in to fill the gap.
05:43They exploded into a strange and diverse group.
05:46The earliest were the size of robins.
05:49But over millions of years, some grew as large as a twin-engine plane, with a wingspan of almost 40
05:54feet.
05:55They weighed from a few ounces to 200 pounds.
06:01Most lost their teeth, though some developed rows of bristles, perhaps for filtering food from the water.
06:07The newer model pterodactyloids shared longer heads crowned with magnificent crests that could be up to twice the size of
06:14their bodies.
06:15Their head bones had become very lightweight, and their necks became bird-like, flexible, and strong.
06:21Their tails shrunk to little stumps, no longer useful for flight.
06:25The loss of the long tail heralds an important change for the flying reptiles.
06:31Without it, they depended more on subtle wing adjustments to compensate for changes in air currents during flight,
06:37behavior that implies greater intelligence than the earlier rhamphorhynchoids.
06:45Flying is perhaps the most strenuous evolutionary adaptation ever to arise.
06:52Scientists define two kinds of flying, soaring and flapping.
06:56Soaring flight, which depends on updrafts and breezes, requires less energy than active flapping.
07:02Like bats and birds, pterosaurs had skeletons which accommodated the large flight muscles controlling their oversized wings.
07:11Paleontologist Bob Bakker believes their muscular development indicates pterodactyls were strong flyers.
07:17If you analyze pterodactyls in the front leg, in the back leg, in the torso, there's no animal that's ever
07:24evolved such a complete commitment to powered flight.
07:27Nearly every ounce of body muscle is tied to the flight muscles.
07:31These were exceptionally sophisticated, exceptionally strong flyers.
07:35It takes enormous energy and muscle strength for all that flapping.
07:39That requires a sophisticated metabolism, a warm-blooded metabolism.
07:44It also takes a nimble and sophisticated brain.
07:47Scientists believe pterosaurs had both.
07:50Pterosaurs' commitment to flight was capped by a lightweight but very strong skeleton.
07:59Berkeley paleontologist Kevin Padian is an expert on the evolution of flight and the anatomy of pterosaurs.
08:08First thing to know about pterosaur bones is that they have the thinnest bones of any vertebrates.
08:13This one's squashed completely flat, flat as a pancake.
08:16And it's just like it was run over by an 18-wheeler sometime in the Cretaceous there in the middle
08:21of the ocean, right?
08:21And it's a very, this bone comes from the upper arm like this.
08:26It's squashed completely flat.
08:28The bone wall is so thin, it's about the same dimension as the wall of a dirter.
08:34A dirter is one of those things you get at the end of the paper towels, the cardboard thing in
08:37the middle, you go dir, dir, dir.
08:38Well, that's what this thing is like, except there's nothing in the middle of it.
08:42I mean, it's just completely air-filled and it's squashed flat and the bone walls are very, very thin.
08:48Now, you might think this would make it a very weak bone, but in fact, we checked this out with
08:52some engineers at Stanford,
08:53and we're working with them, and they showed us that, in fact, the big diameter of this arm is what
09:00really makes it strong.
09:01Despite its hollow center, the thickness of the walls of the pterosaur bones enabled them to withstand the forces of
09:07flight.
09:09Calculations show that pterosaur bones are up to 86% stronger than similar mammal bones.
09:17Scientists agree that even the enormous pterosaurs could fly, but how?
09:25Two hundred million years ago, a great sea covered this area in southern Germany.
09:30Animals living along its shore would fall in, die, and become buried by the fine, silty deposits.
09:38Over millions of years, these deposits would harden into a smooth limestone.
09:48For centuries, this limestone had been quarried to make tiles and artist stones.
09:56But in the late 1700s, something unusual was pulled from this quarry, a strange and twisted fossil with the body
10:05and head of a lizard.
10:06Its long, curving fingers were simply incomprehensible, almost dragon-like.
10:11It landed, as interesting fossils of the day often did, on the desk of Georges Cuvier, the brilliant French anatomist.
10:19If restored to life, he wrote, the fossil would resemble nothing in the modern world.
10:24In the early 1800s, a time that knew nothing of extinction, Cuvier's contention was revolutionary.
10:30It was the seed of an idea that would become a fundamental principle of evolutionary theory.
10:37Cuvier named the creature Pterodactylus, or wing finger.
10:41To him, it was clear that this extraordinarily elongated last finger bone has supported some kind of wing.
10:48Scientists tried to explain how a primitive reptile could ever retain the advanced powers of flight.
10:54The verdict was that they could fly, barely, otherwise they'd still be around.
11:05Paleontologist David Unwin, of the University of Bristol, England, has studied the evolution of the pterosaurs.
11:11For many, many years, people thought that it was really a rather poor kind of flyer.
11:16They thought these animals were only capable of hurling themselves from cliffs and crashing to the ground
11:21and then sort of staggering back up again and doing the whole thing over.
11:24At the turn of the century, the English geologist H.G. Seeley wrote a popular book called Dragons of the
11:30Air.
11:31After studying pterodactyls for decades, Seeley argued they were extraordinarily sophisticated, warm-blooded flyers.
11:39His opinions did not prevent the pterodactyls' fall from grace.
11:43Science decided that the first experiment in non-insect flight was an abysmal failure.
11:50Professor Seeley at Cambridge in the 1870s had a magnificent monograph about pterodactyl joints and how they moved.
11:57And he said these were hot-blooded like birds and powerful flyers, very agile and able critters.
12:02In the 1930s, the pendulum swung and people said they're not hot-blooded.
12:08They didn't have good joints.
12:09They had weak wings.
12:11They just could barely soar in the air and the least little turbulence would send them fluttering around like a
12:17poorly designed Air Force production.
12:19The pterosaurs' flight into obscurity would last almost 50 years.
12:23Then a generation of scientists raised on Hollywood's image of these creatures would take a fresh look at them.
12:32Pterosaurs went from evolutionary failures to pioneers of flight.
12:37It was the first time on Earth that an animal other than insects developed the ability to fly.
12:46The predecessors of these winged reptiles appear about the same time as early dinosaurs, 225 million years ago.
12:54Paul Serino has found some of the earliest fossils ever discovered, pushing back the family tree for dinosaurs and now,
13:02quite possibly, for pterosaurs.
13:06And so we think that pterosaurs are not modified dinosaurs, but arose from a different kind of reptile nearly the
13:13same time.
13:13If you went up to the family tree of dinosaurs and took the whole tree off, pterosaurs would not be
13:19in your hand.
13:20They're outside that.
13:23Scientists have nothing to compare the pterosaurs to.
13:26The only other backbone animals that can fly are birds and bats.
13:30Since the 19th century, paleontologists believe that pterosaur wings were bat-like, leathery, stretching between four elongated fingers and their
13:39feet.
13:40Bats' wings attach to their hind legs, making bats strong flyers, but presenting a burden once they've landed.
13:48On the ground, bats walk on four legs, awkwardly lifting their wings off the ground.
13:56David Unwin supports the bat-like view of pterosaurs.
14:00And basically the hind limbs are sprawling out sideways and the feet are sort of turned right out like this.
14:07And then the forelimbs came down and they had three little fingers and claws on the ends down there.
14:13And they put these down on the ground and they had the enormous great wing finger would be spreading up
14:18round and over the back.
14:19And they moved along rather slowly and very laboriously.
14:23Remember, they have wing membranes attached to their hind limbs and going between their hind limbs.
14:27So they move along quite slowly and laboriously and they certainly didn't move very fast at all when they were
14:33on the ground.
14:35Other scientists believe pterosaurs were two-legged and bird-like with narrow wings attached at the hips,
14:40leaving their hind legs unencumbered for walking.
14:45Paleontologist Kevin Padian demonstrates.
14:48Pterosaurs walk like birds and the other dinosaurs.
14:51And the reason we know this is they have their pelvis and their hind limbs set up like the feet
14:56of dinosaurs and birds.
14:57They have thigh bones in which the head of the thigh, the femur, comes right into the socket like this.
15:03Very much like our femora.
15:05Now, if you just look at our femora, which has this big ball and socket joint,
15:09we could stick our legs out like this and we could walk like that.
15:12But in fact we don't do that. How do we know that? We look at the rest of the leg.
15:15And in pterosaurs and birds, they have this femur that goes out like this,
15:19and they have a knee joint here.
15:21They have very long shin bones.
15:23They have an ankle that only works like a hinge in this direction.
15:26So they have to walk pretty much like this, very much like birds do.
15:30And they also walk on their toes.
15:32So they put one foot in front of the other.
15:34They're slightly towed inwards, like birds, like dinosaurs.
15:38The fossil record doesn't contain a perfectly preserved soft tissue imprint
15:42that could answer the question of bird-like or bat-like anatomy.
15:46Paleontologist Chris Bennett feels that comparisons to birds and bats
15:50will never sufficiently explain the remarkable fossils of the pterosaurs.
15:57I think we could learn a lot about pterosaurs by comparing them to the living flying animals, birds and bats.
16:04But I also think that pterosaurs are as different from birds as they are from bats.
16:09And probably as different from those two as birds and bats are different from each other.
16:14I think basically pterosaurs are pterosaurs.
16:20Though our picture of pterosaurs has changed with new evidence,
16:23their place in our imaginations has never wavered.
16:26Bob Baca has followed the pterosaurs trajectory through science and popular culture.
16:32I like pterodactyls.
16:33A lot of people like pterodactyls.
16:36How scientists view pterodactyls has gone in a complete circle.
16:43The most exciting thought about pterodactyls is this.
16:46Watch a movie with good pterodactyls.
16:49Watch King Kong.
16:49You know, the pteranodon that tried to eat Fey Ray,
16:52this great big, black, harpy-ish, ugly pterodactyl comes down,
16:56grabs Fey Ray and she screams and King Kong saves her.
16:59What we're realizing now is something awfully obvious.
17:02Pterodactyls weren't grey.
17:03They weren't ugly, bat-like, black monsters.
17:09While the question of wing structure remains unsettled,
17:12scientists look for other clues to pterosaur behavior.
17:16The answers may lie in the Niobrara chalk bed in Kansas,
17:20where the fossils tell a surprisingly detailed story about the lives of the pterosaurs.
17:28For decades, paleontologists recognized that two distinct types of pteranodons
17:33were coming out of the Niobrara chalk beds.
17:36Big ones with 25-foot wingspans and enormous head crests,
17:41and smaller, more numerous ones with modest crests.
17:44For these two different species, Chris Bennett seems to have solved the puzzle.
17:52The large pteranodons had enormous crests, longer than their bodies.
18:00The smaller pteranodons had much more modest crests, but larger pelvic openings.
18:06The fact that they differ only in size and in the size of the cranial crest and in the pelvis
18:13made me think that they were sexes.
18:15And the fact that the small pelvis here has such a large opening makes me think that they're females.
18:21Bennett's analysis of the bones revealed that young pteranodons grew quickly.
18:26From just a few inches inside an egg, they developed to some 20 feet across when ready to leave the
18:32nest.
18:35The implication of this is that they would require considerable parental care.
18:43So their mothers would have to be feeding them, bringing fish and so forth in to feed them.
18:52The development of parental care enabled pteranodon to grow to unprecedented size, with a wingspan of more than 23 feet.
19:00But pteranodon was dwarfed by what came later.
19:10In 1972, a pterosaur emerged from the Texas Badlands that would set the scientific community abuzz.
19:16A giant with the tongue-twisting name of Quetzalcoatlus.
19:22It was named after the Aztec deity depicted as a feathered servant.
19:29Known from a single enormous fossilized wing bone, Quetzalcoatlus was one of the last and perhaps the greatest of the
19:36flying reptiles.
19:37It lived around 70 million years ago, in the Cretaceous period, the end of the age of the dinosaurs.
19:46In the Cretaceous, the area that is now Big Bend, Texas was a floodplain, fed by a system of rivers.
19:56The landscape was sandy and sparsely forested.
19:59Quetzalcoatlus eked out a living, probing the shallows for crabs and mollusks, which it would crack with its strong toothless
20:06beak.
20:13Quetzalcoatlus may also have lived like a vulture, scavenging meat from drowned animals.
20:22In full flight, Quetzalcoatlus would have been the size of a military aircraft with a wingspan of 39 feet and
20:28weighing up to 200 pounds.
20:30But the discovery reopened an old question.
20:33Had evolution played a trick on pterosaurs, making them too big to fly?
20:43In 1985, Paul McCready, an aeronautical engineer and a team of scientists, attempted the impossible to build a flying model
20:52of the world's largest pterosaur.
20:57Quetzalcoatlus would be the largest flying animal of all time, if it could get off the ground.
21:03McCready's prototypes, designed as gliders, launched easily.
21:12But they were not successful.
21:23McCready looked to nature.
21:25Flapping wings had to be the answer.
21:30Instead of muscles, McCready used computerized motors to simulate Quetzalcoatlus flight.
21:38The 44-pound robotic reptile could flap and twist its wings, spread its digits, and tilt its head to compensate
21:46for wind conditions.
21:48But could technology reproduce what nature perfected?
21:54At the end of 1985, in Death Valley, California, Quetzalcoatlus made its debut.
22:02And for the first time in 65 million years, a pterosaur's shadow crossed the Earth.
22:10Though McCready's model of Quetzalcoatlus was half its size and one-fourth the weight of the living pterosaur,
22:16it proved that the giant's body plan made it a powerful flyer.
22:42Pterosaurs survived for more than 150 million years throughout the age of dinosaurs.
22:48Pterosaurs survived for more than 150 million years throughout the age of dinosaurs.
22:51They vanished.
22:54Some scientists have suggested that the high winds brought on by the changing climate at the end of the Cretaceous
23:00literally blew the pterosaur into extinction.
23:03Some suppose they were simply out-competed by birds.
23:07It may have been a matter of size.
23:12When the pterodactyls suffered their final extinction, they were all big.
23:15I mean, really big.
23:16They were in that upper zone of mobile big critters that suffer extinction.
23:22Birds, meanwhile, include a great variety of small and medium species.
23:26So, they sailed through the extinction.
23:28They survived.
23:29They were below the threshold.
23:30Pterodactyls were all above the threshold and got knocked out.
23:38They were below the threshold.
23:38Only in the imagination of science does the pterosaur darken the skies.
23:50What we learn about these goliaths of free history sheds light not upon our realm, but theirs.
23:57A dim and hazy world that we can only imagine.
24:03Through flights of fancy.
24:06Wow.
24:07Thank you very much.
24:34Good morning.
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