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PASSAGE 4
*The fossil remains of the first flying vertebrates, the pterosaurs, have intrigued paleontologists for more than two centuries. How such large creatures, which weighed in some cases as much as a piloted hang-glider
5) and had wingspans from 8 to 12 meters, solved the problems of powered flight, and exactly what these creatures were--reptiles or birds-are among the ques-tions scientists have puzzled over.
* Perhaps the least controversial assertion about the
10) pterosaurs is that they were reptiles. Their skulls,pelvises, and hind feet are reptilian. The anatomy of their wings suggests that they did not evolve into the class of birds. In pterosaurs a greatly elongated fourth finger of each forelimb supported a winglike membrane.
15) The other fingers were short and reptilian, with sharp claws. In birds the second finger is the principal strut of the wing, which consists primarily of feathers. If the pterosaurs walked on all fours, the three short fingers may have been employed for grasping. When a
20) pterosaur walked or remained stationary, the fourth finger, and with it the wing, could only turn upward in an extended inverted V-shape along each side of the animal's body.
* The pterosaurs resembled both birds and bats in
25) their overall structure and proportions. This is not sur- prising because the design of any flying vertebrate is subject to aerodynamic constraints. Both the pterosaursand the birds have hollow bones, a feature that repre-sents a savings in weight. In the birds, however, these
30) bones are reinforced more massively by internal struts.
*Although scales typically cover reptiles, the pterosaurs probably had hairy coats. T.H. Huxley rea-soned that flying vertebrates must have been warm-blooded because flying implies a high rate of
35) metabolism, which in turn implies a high internal tem-perature. Huxley speculated that a coat of hair would insulate against loss of body heat and might streamline the body to reduce drag in flight. The recent discoveryof a pterosaur specimen covered in long, dense, and
40) relatively thick hairlike fossil material was the first clearevidence that his reasoning was correct.
*Efforts to explain how the pterosaurs became air-borne have led to suggestions that they launched them-selves by jumping from cliffs, by dropping from trees.
45) or even by rising into light winds from the crests of waves. Each hypothesis has its difficulties. The first wrongly assumes that the pterosaurs' hind feet rese-mbled a bat's and could serve as hooks by which the animal could hang in preparation for flight. The second
50) hypothesis seems unlikely because large pterosaurs could not have landed in trees without damaging their wings. The third calls for high waves to channelupdrafts. The wind that made such waves however,might have been too strong for the pterosaurs to
55) control their flight once airborne.
7. It can be inferred from the passage that somescientists believe that pterosaurs
(A) lived near large bodies of water
(B) had sharp teeth for tearing food
(C) were attacked and eaten by larger reptiles
(D) had longer tails than many birds
(E) consumed twice their weight daily to maintaintheir body temperature
答案是A。请问是通过文章中那句话推导出来的。我选了E，虽然也不觉得是正确答案。 |
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发表于 2010-3-13 16:19:55
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