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.
2017年奥斯卡:《冰雪奇缘》获得最佳动画长片
国内英语资讯:Chinas 11th Ethnic Games opens in Zhengzhou
恐怖袭击逃生指南:RUN! HIDE! FIGHT!
手机选择调查:女人偏爱苹果 男人钟情三星
比特币之父中本聪首曝光 隐居美国加州
耐克又推出新的限量鞋子
天才指挥家:小萌娃全情投入指挥唱诗班
精彩短片:5分钟浓缩恋爱全过程
女人因什么而快乐 你懂她吗
奥斯卡效应:获奖者比候选者长寿?
第86届奥斯卡金像奖完整获奖名单
女人必知 男人最爱的那9种女人
萌化了:大熊猫圆圆哄宝宝睡觉(视频)
三月看两会:让梦想照入现实
国际英语资讯:Triple polls boost for British PM Johnson as political scraps continue over Brexit
普京、斯诺登获2017年度诺贝尔和平奖提名
亚洲部分国家加入马来西亚航班救援
国际英语资讯:Kuwait-U.S. summit postponed as Kuwaiti emir continues medical tests
国际英语资讯:No peace talk would work with continued Taliban violence: Afghan govt
国内英语资讯:400 photos, short videos on display to mark 70th anniversary of PRC founding
“小金人”背后的秘密
2017年奥斯卡:最佳演员们谁最惴惴不安?
睡觉时手机放旁边,是不是很危险?
国内英语资讯:1 dead, 63 injured in Sichuan quake
爱在雾霾天:北京情侣戴防毒面具拍婚纱照
可以巩固男女感情的化学反应
流浪汉买彩票中1720万大奖 暴富后救助他人
为啥妈妈老嫌爸爸家务干得少
畅想十年后的中国
体坛英语资讯:Federer knocked out of Cincinnati Masters by world No. 70 Rublev
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |