托福阅读真题Official 48 Passage 2（三）

托福阅读真题Official 48 Passage 2（三）

Determining Dinosaur Diet

Determining what extinct dinosaurs ate is difficult,but we can infer some aspects of their dietary preferences.Traditionally,this information has been derived from direct evidence,such as stomach contents,and indirect evidence,such as establishing a correlation between particular body characteristics and diets of living animals and then inferring habits for dinosaurs.

Animals such as house cats and dogs have large,stabbing canine teeth at the front of the mouth and smaller,equally sharp teeth farther back in their jaws.Many of these animals are also armed with sharp claws.The advantage of teeth and claws as predatory tools is obvious.Now consider animals like cows,horses,rabbits,and mice.These animals have flat teeth at the back of the jaw that are analogous to and have the same function as grindstones.Unlike the meat-slicing and stabbing teeth of carnivores,the teeth of these animals grind and shred plant material before digestion.

More clues exist in other parts of the skull.The jaw joint of carnivores such as dogs and cats has the mechanical advantage of being at the same level as the tooth row,allowing the jaws to close with tremendous speed and forcing the upper teeth to occlude against the lower teeth with great precision.In herbivorous animals,rapid jaw closure is less important.Because the flat teeth of herbivores work like grindstones,however,the jaws must move both side to side and front to back.The jaw joints of many advanced herbivores,such as cows,lie at a different level than the tooth row,allowing transverse tearing,shredding,and compression of plant material.If we extend such observations to extinct dinosaurs,we can infer dietary preferences(such as carnivory and herbivory),even though we cannot determine the exact diet.The duck-billed dinosaurs known as hadrosaurs are a good example of a group whose jaw joint is below the level of the tooth row,which probably helped them grind up tough,fibrous vegetation.

Paleontologists would like to be much more specific about a dinosaur’s diet than simply differentiating carnivore from herbivore.This finer level of resolution requires direct fossil evidence of dinosaur meals.Stomach contents are only rarely preserved,but when present,allow us to determine exactly what these animals were eating.

In the stomach contents of specimens of Coelophysis(a small,long-necked dinosaur)are bones from juvenile animals of the same species.At one time,these were thought to represent embryonic animals,suggesting that this small dinosaur gave birth to live young rather than laying eggs.Further research indicated that the small dinosaurs were too large and too well developed to be prehatchling young.In addition,the juveniles inside the body cavity were of different sizes.All the evidence points to the conclusion that these are the remains of prey items and that,as an adult,Coelophysis was at least in part a cannibal.

Fossilized stomach contents are not restricted to carnivorous dinosaurs.In a few rare cases,most of them“mummies”(unusually well preserved specimens),fossilized plant remains have been found inside the body cavity of hadrosaurs.Some paleontologists have argued that these represent stream accumulations rather than final meals.The best known of these cases is the second Edmontosaurus mummy collected by the Sternbergs.In the chest cavity of this specimen,which is housed in the Senckenberg Museum in Germany,are the fossil remains of conifer needles,twigs,seeds,and fruits.Similar finds in Corythosaurus specimens from Alberta,Canada,have also been reported,indicating that at least two kinds of Late Cretaceous hadrosaurs fed on the sorts of trees that are common in today’s boreal woodlands.

A second form of direct evidence comes from coprolites(fossilized bodily waste).Several dinosaur fossil localities preserve coprolites.Coprolites yield unequivocal evidence about the dietary habits of dinosaurs.Many parts of plants and animals are extremely resistant to the digestive systems of animals and pass completely through the body with little or no alteration.Study of coprolites has indicated that the diets of some herbivorous dinosaurs were relatively diverse,while other dinosaurs appear to have been specialists,feeding on particular types of plants.The problem with inferring diets from coprolites is the difficulty in accurately associating a particular coprolite with a specific dinosaur.

Question 5 of 14

The word“compression”in the passage is closest in meaning to

A.destruction

B.crushing

C.swallowing

D.removal

正确答案：B

题目详解

题型分类：词汇题

选项分析：

B选项crushing压榨，压缩。原文中compression与tearing，shredding并列，可以推断，compression压缩是正确的。

A选项destruction毁灭。

C选项swallowing吞。

D选项removal离开。

Question 6 of 14

According to paragraphs 3 and 4,what can studies of living animals help scientists determine about individual dinosaurs?

A.How the overall jaw size of a given dinosaur species relates to the type of food the species members ate

B.Whether a given dinosaur generally ate plants or generally ate meat

C.How much food a given dinosaur would have needed to eat to remain healthy

D.How an inadequate diet may have affected a given dinosaur’s skull and jaw

正确答案：B

题目详解

题型分类：事实信息题

原文定位：利用题干living animal定位到原文倒数第三句，从这句开始意思是先研究了高级食草动物牛的特点，回答不了题干问题继续往后读，后面一句马上利用这个研究说extend such observation可以研究出恐龙的饮食偏好（食草还是食肉）最后一句细致的描述了鸭嘴龙这种恐龙他们的颌骨在牙齿的下面，能够帮助他们磨碎坚硬的纤维植被。

选项分析：

B选项高度概括的一个选项，意思是恐龙吃草还是吃肉，研究恐龙的食性要从现代的动物入手，所以，研究现代动物的目的只有一个，那就是决定恐龙的食性，正确。

A选项没有提到overall jaw size无中生有。

C选项没有提到吃多少食物。

D选项没有提到inadequate。

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