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1、A team of Ludwig-Maximilians-Universitaet (LMU) in Munich has identified the first fossil specimens1 of a major group of killifishes that is widely distributed in freshwater habitats today. The 6-million-year-old material sheds new light on the evolution of the bony fishes. Killifish are true surviv
2、ors2. These colorful little fish are perfectly3 adapted to the demands of their ephemeral habitats. They spend their short lives in temporary freshwater pools that form during the rainy season, and owe their long-term survival to the fact that their eggs are resistant4 to desiccation. Although they
3、are a species-rich group, and are widely distributed in the tropics and subtropics, their fossil record is sparse5. But now LMU palaeontologists Professor Bettina Reichenbacher and Melanie Altner have identified the first fossil representatives of one of the two extant suborders of killifish. The sp
4、ecimens are exceptionally well preserved, date from about 6 million years ago, and were discovered in Kenya by French palaeoanthropologists, says Reichenbacher. Our studies have now shown that they are members of a previously6 unknown genus that is now extinct, which we have named Kenyaichthys - the
5、 fish from Kenya.A cache that includes 77 complete specimensThe fossils originate from a site located in the Tugen Hills, which lie in the Eastern arm of the East African Rift7 Valley. During the Late Miocene - about six million years ago - the site formed part of a lake, and the newly described spe
6、cimens, each 2 to 4 cm long, were preserved in the sediment8 beds that accumulated on the lake bottom. The sample comprises a total of 169 individuals, and 77 of these are complete, says Altner. The anatomical details discernible in the impressions left in the sediments9 enabled the two researchers
7、to conclusively10 identify all of these individuals as killifishes. Analysis of the structures of the tailfin, the pelvic fins11 and the bones in the skull12, in particular, yielded crucial information that convinced us that this material constituted the first fossils attributable to the killifish S
8、uborder Aplocheiloidei. This group also encompasses13 modern African killifishes, such as Pachypanchax from Madagascar, the striped panchaxes of Southeast Asia and the rivulids of South America, Altner explains.In addition to the fossil aplocheiloids, only a few other freshwater forms were found at
9、the site. Reichenbacher and Altner assume that the prevailing14 environmental conditions were too extreme for less specialized15 species. During the Late Miocene, the climate got drier and extensive areas of savannah developed. We believe that, like modern killifish species, Kenyaichthys was well eq
10、uipped to survive long periods of drought, and could cope better with such conditions than other species of fish, says Reichenbacher.词汇解析：1 specimens n.样品( specimen 的名词复数 )；范例；（化验的）抽样；某种类型的人参考例句：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 som
11、e 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2 survivors 幸存者，残存者，生还者( survivor 的名词复数 )参考例句：The survivors were adrift in a lifeboat for six days. 幸存者在救生艇上漂流了六天。survivors clinging to a raft 紧紧抓住救生筏的幸存者3 perfectly adv.完美地，无可非议地，彻底地参考例句：The witnesses were each perfectly certai
12、n of what they said.证人们个个对自己所说的话十分肯定。Everything that were doing is all perfectly above board.我们做的每件事情都是光明正大的。4 resistant adj.(to)抵抗的，有抵抗力的参考例句：Many pests are resistant to the insecticide.许多害虫对这种杀虫剂有抵抗力。They imposed their government by force on the resistant population.他们以武力把自己的统治强加在持反抗态度的人民头上。5 spar
13、se adj.稀疏的，稀稀落落的，薄的参考例句：The teachers house is in the suburb where the houses are sparse.老师的家在郊区，那里稀稀拉拉有几处房子。The sparse vegetation will only feed a small population of animals.稀疏的植物只够喂养少量的动物。6 previously 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
14、 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。7 rift n.裂口，隙缝，切口；v. 裂开，割开，渗入参考例句：He was anxious to mend the rift between the two men.他急于弥合这两个人之间的裂痕。The sun appeared through a rift in the clouds.太阳从云层间隙中冒出来。8 sediment n.沉淀，沉渣，沉积( 物)参考例句：The sediment settled and the w
15、ater was clear.杂质沉淀后，水变清了。Sediment begins to choke the channels opening.沉积物开始淤塞河道口。9 sediments 沉淀物( sediment 的名词复数 )； 沉积物参考例句：When deposited, 70-80% of the volume of muddy sediments may be water. 泥质沉积物沉积后，体积的 70-80是水。Oligocene erosion had truncated the sediments draped over the dome. 覆盖于穹丘上的沉积岩为渐新世侵
16、蚀所截削。10 conclusively adv.令人信服地，确凿地参考例句：All this proves conclusively that she couldnt have known the truth. 这一切无可置疑地证明她不可能知道真相。 来自简明英汉词典From the facts,he was able to determine conclusively that the death was not a suicide. 根据这些事实他断定这起死亡事件并非自杀。 来自简明英汉词典11 fins 医散热片；鱼鳍；飞边；鸭掌参考例句：The level of TNF- positively correlated with BMI,FPG,HbA1C,TG,FINS and IRI,but not with SBP and DBP. TNF-水平与 BMI、FPG 、HbA1C、TG、FINS 和 IRI 呈显著正相关，与 SBP、DBP 无相关。
