华盛顿大学研究小组发现恐龙进化史的一些小秘密-凯发k8官网

华盛顿大学研究小组发现恐龙进化史的一些小秘密
文章来源:未知 文章作者:meng 发布时间:2010-01-29 00:39 字体: [ ] 
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a george washington university expedition to the gobi desert戈壁大沙漠 of china has enabled researchers to solve the puzzle of how one group of 2 came to look like birds independent of独立的,不受约束的 birds. the discovery extends the fossil record of the family alvarezsauridae – a bizarre奇异的 group of bird-like dinosaurs with a large claw on the hand and very short, powerful arms – back 63 million years, further distancing the group from birds on the 3 tree. until now, there was no direct evidence that dinosaurs of this type lived during the late jurassic侏罗纪, approximately 160 million years ago. george washington university doctoral博士的 candidate jonah choiniere named the newly discovered species of 1, haplocheirus sollers (meaning simple, skillful hand). mr. choiniere's research is featured in the jan. 29 issue of the journal science. "haplocheirus is a transitional过渡期的,变迁的 fossil, because it shows an early evolutionary step in how the bizarre hands of later alvarezsaurs evolved from earlier predatory食肉的,掠夺的 dinosaurs," said mr. choiniere. "the fossil also confirms our predictions that alvarezsauridae should have been evolving in the late jurassic time period."

the fossil of the new species contains several distinguishing features that link it to alvarezsauridae, the family of dinosaurs that includes species such as mononykus (meaning one claw) and that was 4 thought to be a flightless offshoot分支,支流 of ancient birds due to skeletal骨骼的 similarities. despite the similarity between the skeletons, mr. choiniere's research demonstrates that the family alvarezsauridae evolved in parallel并行的,平行的 to birds and did not 5 from起源于 them. the new species shows some of the earliest evolutionary stages in the development of a short, powerful arm with a single 6 claw that may have been used for digging 7白蚁类.

the late jurassic is an important time period for bird evolution, as evidence suggests that birds first evolved from theropod兽脚类的食肉恐龙, or bird-footed, dinosaurs at that time. paradoxically自相矛盾地, fossils of dinosaurs closely related to birds from this time period are extremely rare, furthering the importance of mr. choiniere's work.

the ten-foot long, nearly complete skeleton of haplocheirus sollers 8 was found preserved in river-lain rock in the xinjiang 9 region of northwestern china, a region well-known for its late jurassic fossils. it was collected in 2004 during a series of expeditions to xinjiang co-led by dr. james clark of gw and dr. xu xing of the chinese academy of sciences' institute of vertebrate paleontology and paleoanthropology, co-authors on the report. these expeditions were extremely successful, resulting in the discovery of a small, agile敏捷的,活泼的 relative of crocodilians鳄目动物 (junggarsuchus sloani); the oldest horned dinosaur (yinlong downsi); one of the oldest tyrannosaurs霸王龙 (guanlong wucaii); and several skeletons of an unusual, toothless new ceratosaurian dinosaur (limusaurus inextricabilis) that were buried while stuck in mud pits泥浆池. these discoveries were described in a tv documentary by national 11 ("dino death trap") and a june 2009 article in national geographic magazine.

"the primary goal of our expeditions was to find evidence of the theropod dinosaurs closest to birds, and the discovery of haplocheirus is one of our major discoveries," said dr. clark. "this spectacular skeleton shows how the strange arms of mononykus and other alvarezsaurs evolved from a more typically theropod grasping hand."

theropod dinosaurs include charismatic, meat-eaters like tyrannosaurus rex but also modern birds. alvarezsaurs are one of several groups of theropods closely related to birds, including well-known species like velociraptor迅猛龙.

this research was funded by the national science foundation (nsf) division of earth sciences, the national geographic society, the chinese national science foundation and the george washington university.

"this nsf-supported research sheds light on阐明,解释 the poorly understood early evolution of birds in the late jurassic in china by eliminating alvarezsaurids as ancestors of the birds," said h. richard lane, program director in the national science foundation (nsf)'s division of earth sciences.

mr. choiniere is a student of james clark, the ronald b. weintraub professor of biology in the george washington university's columbian college of arts and sciences, and first accompanied dr. clark on his excavations挖掘,发掘 in china in 2005.

"faculty/student collaboration合作,通敌 to advance science and foster a better understanding of the world around us is a cornerstone基础,柱石 of our mission," said 14 barratt, dean of the columbian college of arts and sciences. "i applaud the work of dr. clark and mr. choiniere for this truly significant evolutionary finding."



点击收听单词发音收听单词发音  

1 xusxp     
n.恐龙
参考例句:
  • are you trying to tell me that david was attacked by a dinosaur?你是想要告诉我大卫被一支恐龙所攻击?
  • he stared at the faithful miniature of the dinosaur.他凝视著精确的恐龙缩小模型。
2 87f9c39b9e3f358174d58a584c2727b4     
n.恐龙( dinosaur的名词复数 );守旧落伍的人,过时落后的东西
参考例句:
  • the brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
  • dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》
3 ctqz7m     
adj.进化的;演化的,演变的;[生]进化论的
参考例句:
  • life has its own evolutionary process.生命有其自身的进化过程。
  • these are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。
4 bkzzzc     
adv.以前,先前(地)
参考例句:
  • the bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
  • let me digress for a moment and explain what had happened previously.让我岔开一会儿,解释原先发生了什么。
5 descend     
vt./vi.传下来,下来,下降
参考例句:
  • i hope the grace of god would descend on me.我期望上帝的恩惠。
  • we're not going to descend to such methods.我们不会沦落到使用这种手段。
6 5hmxa     
adj.为实用而设计的,具备功能的,起作用的
参考例句:
  • the telephone was out of order,but is functional now.电话刚才坏了,但现在可以用了。
  • the furniture is not fancy,just functional.这些家具不是摆着好看的,只是为了实用。
7 8ee357110f82dc8b267190e430924662     
n.白蚁( termite的名词复数 )
参考例句:
  • termites are principally tropical in distribution. 白蚁主要分布在热带地区。 来自辞典例句
  • this spray will exterminate the termites. 这种喷剂能消灭白蚁。 来自辞典例句
8 xvtwm     
n.样本,标本
参考例句:
  • you'll need tweezers to hold up the specimen.你要用镊子来夹这标本。
  • this specimen is richly variegated in colour.这件标本上有很多颜色。
9 dpyyv     
adj.自治的;独立的
参考例句:
  • they proudly declared themselves part of a new autonomous province.他们自豪地宣布成为新自治省的一部分。
  • this is a matter that comes within the jurisdiction of the autonomous region.这件事是属于自治区权限以内的事务。
10 ix2za     
adj.敏捷的,灵活的
参考例句:
  • she is such an agile dancer!她跳起舞来是那么灵巧!
  • an acrobat has to be agile.杂技演员必须身手敏捷。
11 tgsxb     
adj.地理学的,地理的
参考例句:
  • the city's success owes much to its geographic position. 这座城市的成功很大程度上归功于它的地理位置。 来自《简明英汉词典》
  • environmental problems pay no heed to these geographic lines. 环境问题并不理会这些地理界限。 来自英汉非文学 - 环境法 - 环境法
12 185c90d3198bc18760370b8a86c53f51     
n.挖掘( excavation的名词复数 );开凿;开凿的洞穴(或山路等);(发掘出来的)古迹
参考例句:
  • the excavations are open to the public. 发掘现场对公众开放。
  • this year's excavations may reveal ancient artifacts. 今年的挖掘可能会发现史前古器物。 来自辞典例句
13 bw7yd     
n.合作,协作;勾结
参考例句:
  • the two companies are working in close collaboration each other.这两家公司密切合作。
  • he was shot for collaboration with the enemy.他因通敌而被枪毙了。
14 p3fzi     
n.木栓,木钉;vt.用木钉钉,用短桩固定
参考例句:
  • hang your overcoat on the peg in the hall.把你的大衣挂在门厅的挂衣钩上。
  • he hit the peg mightily on the top with a mallet.他用木槌猛敲木栓顶。
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