文章来源:未知 文章作者:meng 发布时间:2010-05-14 02:25 字体: [ ]  进入论坛

Paleontologists(古生物学者) have discovered a rich array of exceptionally preserved(保藏的,腌制的) fossils of marine1 animals that lived between 480 million and 472 million years ago, during the early part of a period known as the Ordovician(奥陶纪) . The specimens2 are the oldest yet discovered soft-bodied fossils from the Ordovician, a period marked by intense biodiversification. The findings, which appear in the May 13 issue of the journal Nature, greatly expand our understanding of the sea creatures and ecosystems4 that existed at a crucial point in evolutionary5 history, when most of the animal life on the planet was found in the oceans. The team—led by Peter Van Roy, a Yale postdoctoral associate, and Derek Briggs, the Frederick William Beinecke Professor of Geology & Geophysics and director of the Yale Peabody Museum of Natural History—uncovered more than 1,500 fossils of soft-bodied marine animals(海洋动物) in newly discovered sites in southeastern Morocco during a field expedition last year. Many are complete fossils, and include sponges(海绵) , annelid(环节动物) worms, mollusks(软体动物) and horseshoe crabs—in particular, a species similar to today's horseshoe crab6, which appeared some 30 million years earlier than previously7 known.

The Cambrian period, known for the "Cambrian Explosion" that saw the sudden appearance of all the major animal groups and the establishment of complex ecosystems, was followed by the "Great Ordovician Biodiversification Event," when the number of marine animal genera(种,类) increased exponentially over a period of 25 million years.

Because hard shells fossilize and are preserved more readily than soft tissue, scientists had an incomplete and biased8(有偏见的) view of the marine life that existed during the Ordovician period until now.

"The early Ordovician was a critical moment when massive diversification3(多样化,变化) takes off, but we were only seeing a small piece of the picture that was based almost exclusively(专有地,排外地) on the shelly fossil record," Briggs said. "Normal faunas9(动物群) are dominated by the soft-bodied organisms we knew were missing, so these exceptionally well-preserved fossils have filled in much of the missing picture."

The site in Morocco where the fossils were discovered was conducive10 to preserving even the soft tissues of the creatures that lived in its waters so long ago, thanks to generally calm waters, occasional(偶然的,临时的) rapid burial that protected the animals from scavengers(清道夫,食腐动物) , and favorable chemical conditions within the sediment11 that allowed for the rapid mineralization of soft tissue as it decayed(腐烂,衰退) .

In addition to providing a more complete understanding of marine life at that time, the team's discovery upends a long-held belief that so-called Burgess Shale-type faunas, which are typical for the Early to Middle Cambrian, disappeared at the end of the Middle Cambrian epoch12, some 499 million years ago.

"There was an anomaly(不规则,异常) in the fossil record. Most of these animals just seemed to disappear at the end of the Middle Cambrian," said Van Roy, first author of the paper.

The team found that these Burgess Shale-type species survived well into the Ordovician period, which would have had a major impact on those ecosystems and their evolution, Van Roy said.

The team expects to find even more fossils representing other species during future planned expeditions in Morocco. "We're only scratching the surface," Van Roy said. "I'm certain there will be more spectacular(壮观的,惊人的) fossils coming out of this site in the near future."


1 marine 77Izo     
  • 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。
2 specimens 91fc365099a256001af897127174fcce     
n.样品( specimen的名词复数 );范例;(化验的)抽样;某种类型的人
  • Astronauts have brought back specimens of rock from the moon. 宇航员从月球带回了岩石标本。
  • The traveler brought back some specimens of the rocks from the mountains. 那位旅行者从山上带回了一些岩石标本。 来自《简明英汉词典》
3 diversification 8scxf     
  • The seminar was to discuss diversification of agriculture. 该研讨会讨论的是农业多种经营。 来自辞典例句
  • Firm diversification is increasingly achieved by the means of takeover and merger. 通过接管和兼并,厂商经营范围日益多样化。 来自辞典例句
4 ecosystems 94cb0e40a815bea1157ac8aab9a5380d     
n.生态系统( ecosystem的名词复数 )
  • 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
5 evolutionary Ctqz7m     
  • 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 crab xoozE     
  • I can't remember when I last had crab.我不记得上次吃蟹是什么时候了。
  • The skin on my face felt as hard as a crab's back.我脸上的皮仿佛僵硬了,就象螃蟹的壳似的。
7 previously bkzzzC     
  • 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。
8 biased vyGzSn     
  • a school biased towards music and art 一所偏重音乐和艺术的学校
  • The Methods: They employed were heavily biased in the gentry's favour. 他们采用的方法严重偏袒中上阶级。
9 faunas 1945a7981e63bcd2918b213ca96dbf4d     
  • Brackish waters generally support only a small range of faunas. 咸水水域通常只能存活为数不多的几种动物。
  • We shall appreciate this difficulty more clearly, by looking to certain existing faunas and floras. 通过观察某些现存的动物群和植物群,我们就能更清楚地了解这种困难了。
10 conducive hppzk     
  • This is a more conducive atmosphere for studying.这样的氛围更有利于学习。
  • Exercise is conducive to good health.体育锻炼有助于增强体质。
11 sediment IsByK     
  • The sediment settled and the water was clear.杂质沉淀后,水变清了。
  • Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。
12 epoch riTzw     
  • The epoch of revolution creates great figures.革命时代造就伟大的人物。
  • We're at the end of the historical epoch,and at the dawn of another.我们正处在一个历史时代的末期,另一个历史时代的开端。
TAG标签: animals fossils Marine