科学家首次发现霸王龙在南半球存在的证据-凯发k8官网

科学家首次发现霸王龙在南半球存在的证据
文章来源:未知 文章作者:meng 发布时间:2010-03-26 05:08 字体: [ ] 
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scientists from cambridge, london and melbourne have found the first ever evidence that tyrannosaur(霸王龙) 2 existed in the southern continents. they identified a 3 bone(髋骨,坐骨) found at 1 4 in victoria, australia as belonging to an ancestor of tyrannosaurus rex. the find sheds new light on the 5 history of this group of dinosaurs. it also raises the crucial question of why it was only in the north that tyrannosaurs evolved into the giant 6(食肉动物,捕食者) like t. rex.

the 30cm-long pubis(趾骨) bone from dinosaur cove looks like a rod(棒) with two expanded ends, one of which is 7 and connects to the hip and the other looks like a 'boot'.

according to dr roger benson of the department of earth sciences at the university of cambridge, who identified the find: "the bone is unambiguously(明白地,不含糊地) identifiable as a tyrannosaur because these dinosaurs have very 8(有特色的,与众不同的) hip bones."

the discovery lays to rest the belief held by some scientists that tyrannosaurs never made it to the southern continents.

"this is an exciting discovery because tyrannosaur fossils had only ever been found in the northern hemisphere(半球) before and some scientists thought tyrannosaurs never made it down south.

"although we only have one bone, it shows that 110 million years ago small tyrannosaurs like ours might have been found worldwide. this find has major significance for our knowledge of how this group of dinosaurs evolved." says dr benson.

dr paul barrett, palaeontologist at the natural history museum, london and member of the research team commented: "the absence of tyrannosauroids from the southern continents was becoming more and more 9(异常的,不规则的) as representatives of other 'northern' dinosaur groups started to show up in the south. this find shows that tyrannosauroids were able to reach these areas early in their evolutionary history and also hints at the possibility that others remain to be discovered in africa, south america and india."

the bone would have come from an animal about three metres long and weighing around 80 kg, similar to a human, and would have had the large head and small arms that make tyrannosaurs so distinctive.

the newly identified dinosaur, known as nmv p186069, was much smaller than t. rex, which was 12 metres long and weighed around four tonnes. giant size like this only evolved late in the tyrannosaur lineage(血统,家系) .

compared with t. rex, which lived about 70 million years ago at the end of cretaceous period, nmv p186069 lived earlier during the cretaceous, around 110 million years ago.

during the time of the dinosaurs the continents gradually went from a single supercontinent towards something like their present-day arrangement. this tyrannosaur is from the mid-stages of this 10 break-up, when the southern continents of south america, antarctica, africa and australia had separated from the northern continents, but had not separated from each other.

while answering the question of whether or not tyrannosaurs lived in both the southern and northern hemispheres, the new find leaves another, deeper mystery: why did tyrannosaurs evolve into giant predators such as t. rex only in the northern hemisphere?

according to dr benson: "it is difficult to explain why different groups succeeded in the north and the south if they originally existed in both places. what we need to know now is just how diverse(不同的,变化的) the early radiation of tyrannosaurs was, why they went extinct, leaving only giant-sized, short-armed species like t. rex, and how successful they might have been in the southern hemisphere. we can only answer these questions with new discoveries."

the paper is published today in science.



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 1doxx     
n.臀部,髋;屋脊
参考例句:
  • the thigh bone is connected to the hip bone.股骨连着髋骨。
  • the new coats blouse gracefully above the hip line.新外套在臀围线上优美地打着褶皱。
4 9y8za     
n.小海湾,小峡谷
参考例句:
  • the shore line is wooded,olive-green,a pristine cove.岸边一带林木蓊郁,嫩绿一片,好一个山外的小海湾。
  • i saw two children were playing in a cove.我看到两个小孩正在一个小海湾里玩耍。
5 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。
6 48b965855934a5395e409c1112d94f63     
n.食肉动物( predator的名词复数 );奴役他人者(尤指在财务或性关系方面)
参考例句:
  • birds and their earthbound predators 鸟和地面上捕食它们的动物
  • the eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。 来自《简明英汉词典》
7 1d5d9fedd9ab44a19d9f30a0b81f79a8     
[医](水)平扁的,弄平的
参考例句:
  • she flattened her nose and lips against the window. 她把鼻子和嘴唇紧贴着窗户。
  • i flattened myself against the wall to let them pass. 我身体紧靠着墙让他们通过。
8 es5xr     
adj.特别的,有特色的,与众不同的
参考例句:
  • she has a very distinctive way of walking.她走路的样子与别人很不相同。
  • this bird has several distinctive features.这个鸟具有几种突出的特征。
9 mwbzi     
adj.反常的;不规则的
参考例句:
  • for years this anomalous behaviour has baffled scientists.几年来这种反常行为让科学家们很困惑。
  • the mechanism of this anomalous vascular response is unknown.此种不规则的血管反应的机制尚不清楚。
10 zazyk     
adj.大陆的,大陆性的,欧洲大陆的
参考例句:
  • a continental climate is different from an insular one.大陆性气候不同于岛屿气候。
  • the most ancient parts of the continental crust are 4000 million years old.大陆地壳最古老的部分有40亿年历史。
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