首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Once found almost entirely in the western United States and in As. ia, dinosaur fossils are now being discovered on all seven co
Once found almost entirely in the western United States and in As. ia, dinosaur fossils are now being discovered on all seven co
admin
2010-03-25
47
问题
Once found almost entirely in the western United States and in As. ia, 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. Witmer was a leading researcher for a study on dinosaur anatomy that was presented at the annual meeting of the Society for Vertebrate Paleontology, which concluded on October 3 in Snowbird, Utah.
Witmer’s study 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 eeratopsians migrated to what is now North America.
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 eight-year-old Christopher Wolfe and his father, 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. Doug Wolfe named’ the important new species of dinosaur Zuniceratops Christopheri after his son.
An expedition from the Universities of Alaska in Anchorage and Fairbanks has discovered a region in remote northern 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 20m (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.
Scientists speculated that the tracks were made at the edge of a lake or swamp and were then hardened and preserved. The rock containing the tracks was then pushed into a vertical position over millions of years of geologic activity. Dinosaur eggs have also been found at the site, which paleontologists are working to preserve before it falls victim to erosion. Paleontologists hope to study the site and learn about the diet and physical characteristics of the dinosaurs that are represented there.
Newly-found fossilized tracks in Alaska proved that dinosaurs’ migration between Asia and North America took place
选项
A、much earlier than experts previously thought.
B、much later than experts previously thought.
C、after Asia became an independent continent.
D、sometime around 25 million years ago.
答案
A
解析
第八段中的第二句"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"表明在阿拉斯加州发现的恐龙痕迹是一亿年以前的。而最后一句说该发现提供了重要的证据,表明亚美大陆之间的恐龙迁移发生在 Cretaceous(白垩纪)时代的早中期。结合上文讲到白垩纪末期在七千万至八千万年前,可以确信,该发现证明这种迁移发生的时间早于以往专家们推断的时间。
转载请注明原文地址:https://kaotiyun.com/show/mTqO777K
0
专业英语八级
相关试题推荐
Intheinformationtechnologyindustry,itiswidelyacknowledgedthathowwellITdepartmentsofthefuturecanfulfiltheirbu
A、Theteamwithabetterluck.B、Theteamwithgoodabilities.C、Theteamwearingred.D、Theteamshowingastrongwill.C
Takingonaleadershiproleforthefirsttimeistough.Thereisalwayspressureonyoutodotherightthings,andtobeseen
A、InLondon,peopleearn£3,000permonthonaverage.B、InBritain,goodlooksoftenleadtohigherincome.C、StudentsinLondon
A、Manufacturers.B、Employees.C、Farmers.D、Pessimists.C
A、Thelawdoesnotspecifyclearlyonsomekeyissues.B、Thelawisinconflictwiththerelevantfederallaws.C、Listeningtoo
A、Whenshehadjustturnedten.B、Aftershefinishedsecondaryschool.C、Whenshewastwelve.D、Whenshewasattheprimaryscho
PlansforoneofBritain’sbiggesthousingdevelopments,of5,000homesworthhundredsofmillionsofpounds,mayhavetobeab
InBritain’soverheatedpropertymarket,theonlythingshotterthanthepricesofthehousesforsalearethefirmsthatbuild
1Humanmigration,thetermisvague.Whatpeopleusuallythinkofisthepermanentmovementofpeoplefromonehometoanot
随机试题
某期权交易所2013年3月20日对ABC公司的期权报价如下:要求:针对以下互不相干的几问进行回答:若丙投资人购买一项看跌期权,标的股票的到期日市价为45元,其此时期权到期价值为多少?投资净损益为多少?
如果领导风格不适应领导情景,菲德勒认为应该()
股骨干与股骨颈构成的颈干角约为
A、芦头B、芦碗C、芋D、珍珠疙瘩E、铁线纹人参根茎上的凹窝状茎痕习称
根据个人所得税法律制度的规定,将个人所得税的纳税义务人区分为居民纳税人和非居民纳税人,依据的标准有()。
一个孢原细胞经过一系列细胞分裂,最终可产生()个卵细胞。
假设一电子设备装有三个同种电气元件,其工作状态相互独立,且无故障工作时间都服从参数为λ(>0)的指数分布.当三个元件都无故障时,电子设备正常工作,否则整个电子设备不能正常工作,则电子设备正常工作的时间丁服从参数为___________的指数分布.
Whataretheytalkingabout?
Afteramonthspentwithme,hewasbeginningtogetveryannoyedatmeaboutmycarelessness.
Thenexttimeyou’retemptedtobuyLipitororsomeothermedicationonline,ponderthis:there’sahighlikelihoodthatwhatyo
最新回复
(
0
)