编辑点评: 研习GRE作文考试的优秀范文不仅可以学到有用的词汇和句子,更能从中学习逻辑的构建方式和作文框架的结构等内容,这里为大家提供GRE的范文,希望对同学们的备考有所帮助。
The preservation of embryos and juveniles is a rate occurrence in the fossil record. The tiny, delicate skeletons are usually scattered by scavengers or destroyed by weathering before they can be fossilized. Ichthyosaurs had a higher chance of being preserved than did terrestrial creatures because, as marine animals, they tended to live in environments less subject to erosion. Still, their fossilization required a suite of factors: a slow rate of decay of soft tissues, little scavenging by other animals, a lack of swift currents and waves to jumble and carry away small bones, and fairly rapid burial. Given these factors, some areas have become a treasury of well-preserved ichthyosaur fossils.
The deposits at Holzmaden, Germany, present an interesting case for analysis. The ichthyosaur remains are found in black, bituminous marine shales deposited about 190 million years ago. Over the years, thousands of specimens of marine reptiles, fish and invertebrates have been recovered from these rocks. The quality of preservation is outstanding, but what is even more impressive is the number of ichthyosaur fossils containing preserved embryos. Ichthyosaurs with embryos have been reported from 6 different levels of the shale in a small area around Holzmaden, suggesting that a specific site was used by large numbers of ichthyosaurs repeatedly over time. The embryos are quite advanced in their physical development; their paddles, for example, are already well formed. One specimen is even preserved in the birth canal. In addition, the shale contains the remains of many newborns that are between 20 and 30 inches long.
Why are there so many pregnant females and young at Holzmaden when they are so rare elsewhere? The quality of preservation is almost unmatched and quarry operations have been carried out carefully with an awareness of the value of the fossils. But these factors do not account for the interesting question of how there came to be such a concentration of pregnant ichthyosaurs in a particular place very close to their time of giving birth.
“请假”英语应该怎么说?
做了这十件事情,你一定会被解雇!
国内英语资讯:China, U.S. to hold talks on strategic security issues
纪念阿加莎·克里斯蒂诞辰125周年
看成语,学英语
新人入职必知Email文化“潜规则”
小学英语阅读之《不守承诺的狼》
小学英语阅读之两位公主
小组面试 问题应该这么答
小学英语阅读练习之The First Question
go的用法总结
怀孕也能臭美:明星准妈妈带火孕妇时尚
国内英语资讯:China condemns terror attack in Pakistan
有效的减压方式
职场启示:前辈给新手高管的10条建议
双语职场:如何融入新工作?
看《生活大爆炸》学英语之这瓶我请
六招助你查出面试后无offer的原因
小学英语手抄报之English club
小学英语手抄报之happy English
辨别易混淆词汇
各种奇葩的密码
国际英语资讯:Chinas Weibo to help microbloggers build their brands
萌娃当道
小学英语阅读理解之究竟丢了谁?
职场新人必看:工作中犯了错怎么办
让中孟合作收获金色果实
“墨西哥”的亡灵节
面试中如何回答“你善于团队合作吗”
国际英语资讯:U.S. remains committed to denuclearization of Korean Peninsula: State Department
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |