咨询电话：400-699-7... 展开

六级网课 词汇 听力 攻略 阅读 零基础

新东方在线 > 六级 > 英语六级备考 > 英语六级口语 > 正文

2019年12月大学英语六级口语经典背诵文章：罕见化石记录

2019-07-22 16:08:25来源：网络

　　新东方在线英语六级频道为大家整理了2019年12月大学英语六级口语经典背诵文章：罕见化石记录，希望可以为备考英语六级的同学们带来帮助，一起来学习一下吧。

　　A Rare Fossil Record

　　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.


大学英语六级寒假全程班

大学英语六级寒假全程班

本文关键字: 英语六级口语

-->

扫码即刻查分 四六级最新答案

四六级好课 海量资料定期更新

更多资料

关注四六级小助手服务号回复【典藏笔记】获取

关注四六级小助手服务号，
获取学习资料

  • 1.打开手机微信【扫一扫】，识别上方二维码；
  • 2.点击【关注公众号】，回复上方关键字领取学习资料。
更多>>
更多内容
更多>>
更多公开课>>
更多>>
更多资料
我要
反馈 返回
首页
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10

京ICP证050421号 京ICP备05067669号-2 京公网安备11010802017616号 网络视听许可证0110531号 京网文(2016)1303-163号

Copyright © 2011-2018 新东方教育科技集团有限公司, All Rights Reserved

违法和不良信息举报电话: 010-81401500 举报邮箱: sec@xdfzx.com 网上有害信息举报专区