Answers For [Recent Tests- VOL] - How a prehistoric predator took to the skies
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[Recent Tests- VOL] - How a prehistoric predator took to the skies
Is that a bird in the sky? A plane? No, it's a pterosaur. Kate Thomas meets Professor Matthew Wilkinson, who built a life-size model to find out how this prehistoric predator ever got off the ground.
Pterosaurs existed from the Triassic period, 220 million years ago, to the end of the Cretaceous period, 65 million years ago, when South America pulled away from Africa and the South Atlantic was formed. 1They are among the least understood of all the extinct reptiles that once spent their lives in the skies while the dinosaurs dominated the land. 2Pterosaurs had no feathers, but at least part of their bodies was covered in hair, not unlike bats. Some believe this is an indication they were warm-blooded. 3Researchers also debate whether pterosaurs travelled on the ground by walking on their hind legs, like birds, or by using all fours, relying on their three-toed front feet as well as their four-toed rear feet.
'Pterosaurs were vertebrates, meaning they were the first flying creatures possessing backbones to become airborne, but scientists have never quite understood their flight technique. 4-11How, they wondered, did such a heavy creature ever manage to take off? 5How could a wing that appears to have been supported by fine, hollow bones have carried one into the sky? Then came the discovery of a site in Brazil's Araripe basin. Here, not just the usual hundreds of fossils of amphibians* and other reptiles found, but archaeologists unearthed a number of very well-preserved pterosaurs. 6The anhanguera – a fish-eating sub-species of pterosaur that ruled the skies in the Cretaceous period – was among them. 'With a wingspan of up to 12 metres, they would have made an amazing sight in the sky – had any human been there to witness it. I've been studying pterosaurs for about eight years now,' says Dr Matthew Wilkinson, a professor of zoology at Cambridge University. With the anhanguera fossil as his model, Wilkinson began gradually reconstructing its skeletal structure in his Cambridge studio. 7The probability of finding three-dimensional pterosaur fossils anywhere is slim. 'That was quite a find,' he says. "Their bones are usually crushed to dust.” Once the structure was complete, it inspired him to make a robot version as a way to understand the animal's locomotion. With a team of model-makers, he has built a remote-controlled pterosaur in his studio. 8“Fossils show just how large these creatures were. I've always been interested in how they managed to launch themselves, so I thought the best test would be to actually build one and try it.
Wilkinson hasn't been alone in his desire to recreate a prehistoric beast. Swiss scientists recently announced they had built an amphibious robot that could walk on land and swim in water using the sort of backbone movements that must have been employed by the first creatures to crawl from the sea. But Wilkinson had the added complication of working out his beast's flight technique. Unlike those of bats or flying squirrels, pterosaur wings – soft, stretchy membranes of skin tissue – are thought to have reached from the chest right to the ankle, reinforced by fibres that stiffened the wing and prevented tearing. Smaller pterosaurs flexed their wings during takeoff. That may have explained the creature's ascent, but it did not answer the most pressing question: how did such enormous creatures manage to launch themselves into the sky? Working with colleagues in London and Berlin, Wilkinson began to piece together the puzzle.
9'It emerged that the anhanguera had an elongated limb called the pteroid. It had previously been thought the pteroid pointed towards the shoulder of the creature and supported a soft forewing in front of the arm. But if that were the case, the forewing would have been too small and ineffectual for flight. 12However, to the surprise of many scientists, fossils from the Araripe basin showed the pteroid possibly faced the opposite way, creating a much greater forewing that would have caught the air, working in the same way as the flaps on the wings of an aeroplane. So, with both feet on the ground, the anhanguera might have simply faced into the wind, spread its wings and risen up into the sky. Initial trials in wind tunnels proved the point – models of pterosaurs with forward-facing pteroids were not only adept at gliding, but were agile flyers in spite of their size. 'This high-lift capability would have significantly reduced the minimum flight speed, allowing even the largest forms to take off without difficulty,' Wilkinson says. 'It would have enabled them to glide very slowly and may have been instrumental in the evolution of large size by the pterosaurs.'
Resting in the grass at the test site near Cambridge, the robot-model's wings ripple in the wind. In flight, the flexible membrane, while much stiffer than the real thing, allows for a smooth takeoff and landing. 10-13But the model is troubled by other mechanical problems. 'Unlike an aircraft, which is stabilised by the tail wings at the back, the model is stabilised by its head, which means it can start spinning around. That's the most problematic bit as far as we're concerned,'10 Wilkinson says. 'We've had to take it flying without the head so far.' When it flies with its head attached, Wilkinson will finally have proved his point.
So what's next for the zoologist — perhaps a full-size Tyrannosaurus rex? 'No,' he tells me: 14'We're desperate to build really big pterosaurs.I'm talking creatures with even greater wingspans, weighing a quarter of a ton. But,' he adds, just as one begins to fear for the safety away and stress levels of pilots landing nearby at Cambridge City Airport, 14'it's more likely we'll start off with one of the smaller, flapping pterosaurs.' This is certainly more reassuring. Let's hope he is content to leave it at that.
*amphibians: animals that can live both in water and on land
Questions 1-6
Complete the summary using the list of words, A-L, below. Write the correct letter, A-L, in boxes 1-6 on your answer sheet.
| A. front feet B. fish C. dinosaurs D. reptiles |
E. flexibility F. hind legs G. amphibians H. birds |
I. strength J. weight K. tail L. hair |
Pterosaurs are believed to have existed until the end of the Cretaceous period. They are classed as 1 (D) which were capable of flight, although, unlike modern species, they had some 2 (L) , which is evidence of their having had warm blood. There are two theories as to how they moved on land: perhaps with all their feet or by using their 3 (F) only. Another mystery has concerned the ability of the pterosaur to fly despite its immense 4 (J) , and the fact that the bones making up the wing did not have great 5 (I) . Thanks to reptile fossils found in Brazil, we now know that the subspecies known as anhanguera had wings that were 12 metres across and that it mainly survived on 6 (B)
Questions 7-10
Do the following statements agree with the claims of the writer in Reading Passage 3?
In boxes 7-10 on your answer sheet, write
YES if the statement agrees with the claims of the writer
NO if the statement contradicts the claims of the writer
NOT GIVEN if it is impossible to say what the writer thinks about this
7
7
It is rare to find a fossil of a pterosaur that clearly shows its skeleton.
8
8
The reason for building the model was to prove pterosaurs flew for long distances.
9
9
It is possible that pterosaur species achieved their wing size as a result of the pteroid.
10
10
Wilkinson has made several unsuccessful replicas of the pterosaur's head.
Questions 11-14
Choose the correct letter, A, B, C or D.
Write the correct letter in boxes 11-14 on your answer sheet.
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