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  3. Once found almost entirely in the western United States and in Asia, dinosau

Once found almost entirely in the western United States and in Asia, dinosau

游客2024-12-27  35
问题     Once found almost entirely in the western United States and in Asia, dinosaur fossils are now being discovered on all seven continents. A host of new revelations emerged in 1998 that promise to reshape scientists’ views of dinosaurs, including what they looked like and when and where they lived.
    It is doubtful that Tyrannosaurus Rex had lips or that Triceratops had cheeks, says Lawrence Witmer, an assistant professor of anatomy at Ohio University in Athens, Ohio. He reached its conclusions by using high-tech computerized axial tomography (CT or CAT) scans along with comparative anatomy studies. For example, the theory that Triceratops and similar dinosaur species had cheeks was based on past comparisons with mammals such as sheep. But Witmer’s careful analysis found the structure of the triceratops jaw and skull made it more likely that Triceratops had a beak like that of an eagle. Witmer said that scientists should use birds and crocodiles as models when researching the appearance of dinosaurs.
    In early October scientists announced that they had confirmed the discovery of a new type of ceratopsian dinosaur. The dinosaur’s bones, found in New Mexico in 1996, are forcing paleontologists to rethink their theories about when ceratopsians migrated to what is now North Arnerica.
    Scientists previously thought that ceratopsians, the group that included the well-known Triceratops, arrived in North America from Asia between 70 million and 80 million years ago. During this time, the late Cretaceous Period, the earth’s two supercontinents—Laurasia in the north and Gondwanaland in the south—were in the process of pulling apart, cutting dinosaur populations off from each other and interrupting migratory patterns.
    The fossilized bones, found by paleontologist Doug Wolfe of the Mesa Southwest Museum in Arizona, date to about 90 million years ago. This could mean that ceratopsians originated in North America and migrated to Asia rather than the reverse, paleontologists said.
    An expedition from the Universities of Alaska in Anchorage and Fairbanks has discovered a region in remote north ern Alaska so rich in fossilized dinosaur tracks that team members dubbed it the " dino expressway". The trampled area was found during the summer of 1998 on Alaska’s North Slope near the Brooks Range.
    The team found 13 new track sites and made casts from the prints of five different types of dinosaurs. The rock in which the prints were found dates to more than 100 million years ago, or about 25 million years older than the previously discovered signs of dinosaurs in the Arctic region. Paleontologists said that the new findings provide important evidence that dinosaurs migrated between Asia and North America during the early and mid-Cretaceous Period, before Asia split off into its own continent.
    Two rich fossil sites in the hills of Bolivia have been recently discovered, exciting paleontologists and dinosaur buffs. This discovery includes one of the most spectacular dinosaur trackways ever found.
    The discovery of a large site in the mountain region of Kila Kila in southern Bolivia was announced in early October. Here scientists found the tracks of at least two unknown species of dinosaur. These included a large quadruped (four- footed) dinosaur that was probably about 20 m (about 70 ft) long.
    The other site, located not far from the Bolivian city of Sucre, was uncovered in a cement quarry by workers several years ago but was not brought to paleontologists’ attention until the middle of 1998. The site features a vertical wall covered with thousands of dinosaur prints representing more than 100 different species. The tracks date back to between 65 million and 70 million years ago. Since dinosaurs are believed to have died out around 65 million years ago, the prints were likely made by some of the last dinosaurs on earth. Paleontologists hope to study the site and learn about the diet and physical characteristics of the dinosaurs that are represented there. [br] The discovery of dinosaur fossil sites in Bolivia is exciting because of the following reasons EXCEPT that______.
选项 A、they are found in a continent other than Asia and North Continent
B、the largest dinosaurs in the world are found in this discovery
C、there are some unknown species of dinosaurs found this time. ,
D、the dinosaurs were believed to be some of the last ones on earth
答案 B
解析 这种EXCEPT题最好的做法就是排除法。C和D很好排除：第八段说在Bolivia地区也发现了恐龙化石，而且这次发现有两个令人激动的发现：the tracts of at least two unknown species of dinosaur和the prints were likely made by some of the last dinosaurs on earth。A的排除赞点劲，但文章第一句就说了：以前只在美国西部和亚洲发现恐龙遗迹，但现在哪都有了。再结合地理常识：玻利维亚在南美，可以推断出A是一个原因，可排除。只有B这个信息文章中没有提到。
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