无齿翼手龙统治着白垩世晚期的天空-凯发k8官网

无齿翼手龙统治着白垩世晚期的天空
文章来源:未知 文章作者:enread 发布时间:2014-08-19 06:57 字体: [ ] 
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a new study provides an exciting insight into the late cretaceous and the diversity and distribution of the toothless 'dragon' pterosaurs(翼手龙) from the azhdarchidae family. the research was published in the open access journal zookeys. the azhdarchidan pterosaurs 1 their name from the persian word for dragon -- aždarha. interestingly, this 2 and rather successful group of pterosaurs included some of the largest known flying animals of all times, with a wingspan reaching between 10 and 12 m.
 
'dragon' pterosaurs had a worldwide distribution once and were the last of their kind to survive on the planet, until some 60 mya. they dominated the skies during the late cretaceus and unlike their 3, were characteristically toothless.
 
"this shift in dominance from toothed to toothless pterodactyloids 4 reflects some fundamental changes in cretaceous 5, which we still poorly understand," comments the author of the study dr alexander averianov, zoological institute of the russian academy of sciences.
 
generally fossil record of pterosaurs is patchy and confined mostly to sedimentary deposits known as konservat-lagerstätten where exceptional depositional conditions facilitated 6 of fragile pterosaur bones. unfortunately, such lagerstätten are very rare for the late cretaceous when most of the 7 history of azhdarchidae took place, which makes these exciting creatures exceptionally hard to study.
 
"azhdarchidae currently represent a real nightmare for paleontologists(古生物学者): most taxa are known from few fragmentary bones, which often do not 8 between named taxa, the few articulated skeletons are poorly preserved, and some of the best available material has remained undescribed for forty years." explains dr averianov about the difficulties studying the group.
 
despite these difficulties, the number of localities were azhdarchidan pterosaurs were found is impressive and 9 reflect the important role they played in the cretaceous ecosystems. these flying giants likely inhabited a large variety of environments, but seem to have been abundant near large lakes and rivers and most common in nearshore 10 environments.


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1 hmlzh     
v.取得;导出;引申;来自;源自;出自
参考例句:
  • we derive our sustenance from the land.我们从土地获取食物。
  • we shall derive much benefit from reading good novels.我们将从优秀小说中获得很大好处。
2 6cddb7353e699051a384686b6b3ff1e2     
vi.起源;由来;衍生;导出v.得到( derive的过去式和过去分词 );(从…中)得到获得;源于;(从…中)提取
参考例句:
  • many english words are derived from latin and greek. 英语很多词源出于拉丁文和希腊文。 来自《简明英汉词典》
  • he derived his enthusiasm for literature from his father. 他对文学的爱好是受他父亲的影响。 来自《简明英汉词典》
3 b59b392832b9ce6825062c39c88d5147     
n.前任( predecessor的名词复数 );前辈;(被取代的)原有事物;前身
参考例句:
  • the new government set about dismantling their predecessors' legislation. 新政府正着手废除其前任所制定的法律。 来自《简明英汉词典》
  • will new plan be any more acceptable than its predecessors? 新计划比原先的计划更能令人满意吗? 来自《简明英汉词典》
4 tmmyq     
adv.显然地;表面上,似乎
参考例句:
  • an apparently blind alley leads suddenly into an open space.山穷水尽,豁然开朗。
  • he was apparently much surprised at the news.他对那个消息显然感到十分惊异。
5 94cb0e40a815bea1157ac8aab9a5380d     
n.生态系统( ecosystem的名词复数 )
参考例句:
  • there are highly sensitive and delicately balanced ecosystems in the forest. 森林里有高度敏感、灵敏平衡的各种生态系统。 来自《简明英汉词典》
  • madagascar's ecosystems range from rainforest to semi-desert. 马达加斯加生态系统类型多样,从雨林到半荒漠等不一而足。 来自辞典例句
6 glnzyu     
n.保护,维护,保存,保留,保持
参考例句:
  • the police are responsible for the preservation of law and order.警察负责维持法律与秩序。
  • the picture is in an excellent state of preservation.这幅画保存得极为完好。
7 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。
8 tkixw     
v.重叠,与…交叠;n.重叠
参考例句:
  • the overlap between the jacket and the trousers is not good.夹克和裤子重叠的部分不好看。
  • tiles overlap each other.屋瓦相互叠盖。
9 mfjz6l     
adv.确实地,无疑地
参考例句:
  • it is undoubtedly she who has said that.这话明明是她说的。
  • he is undoubtedly the pride of china.毫无疑问他是中国的骄傲。
10 77izo     
adj.海的;海生的;航海的;海事的;n.水兵
参考例句:
  • marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
  • when the war broke out,he volunteered for the marine corps.战争爆发时,他自愿参加了海军陆战队。
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