14 A Rare Fossil Record
时间：2018-12-07 作者：英语课 分类：英语范文背诵20篇
14 A Rare Fossil Record
The preservation 1 of embryos 2 and juveniles 3 is a rate occurrence in the fossil record. The tiny, delicate skeletons are usually scattered 4 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 5 animals, they tended to live in environments less subject to erosion. Still, their fossilization required a suite 6 of factors: a slow rate of decay of soft tissues, little scavenging by other animals, a lack of swift currents and waves to jumble 7 and carry away small bones, and fairly rapid burial. Given these factors, some areas have become a treasury 8 of well-preserved ichthyosaur fossils.
The deposits at Holzmaden, Germany, present an interesting case for analysis. The ichthyosaur remains 9 are found in black, bituminous marine shales 11 deposited about 190 million years ago. Over the years, thousands of specimens 13 of marine reptiles 14, fish and invertebrates 15 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 10 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 12 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 16 operations have been carried out carefully with an awareness 17 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.
- The police are responsible for the preservation of law and order.警察负责维持法律与秩序。
- The picture is in an excellent state of preservation.这幅画保存得极为完好。
- Somatic cells of angiosperms enter a regenerative phase and behave like embryos. 被子植物体细胞进入一个生殖阶段，而且其行为象胚。 来自辞典例句
- Evolution can explain why human embryos look like gilled fishes. 进化论能够解释为什么人类的胚胎看起来象除去了内脏的鱼一样。 来自辞典例句
- Do you think that punishment for violent crimes should be the same for juveniles and adults? 你对暴力犯罪的惩罚对于青少年和成人应一样吗？ 来自生活英语口语25天快训
- Juveniles Should we not exactly in need of such strength and conviction? 少年的我们难道不正是需要这种力量和信念吗？ 来自互联网
- Gathering up his scattered papers,he pushed them into his case.他把散乱的文件收拾起来，塞进文件夹里。
- 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。
- She has a suite of rooms in the hotel.她在那家旅馆有一套房间。
- That is a nice suite of furniture.那套家具很不错。
- Even the furniture remained the same jumble that it had always been.甚至家具还是象过去一样杂乱无章。
- The things in the drawer were all in a jumble.抽屉里的东西很杂乱。
- The Treasury was opposed in principle to the proposals.财政部原则上反对这些提案。
- This book is a treasury of useful information.这本书是有价值的信息宝库。
- He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
- The remains of the meal were fed to the dog.残羹剩饭喂狗了。
- We can extract oil from shale.我们可以从页岩中提取石油。
- Most of the rock in this mountain is shale.这座山上大部分的岩石都是页岩。
- Sandstones are, as a rule, interbedded with shales. 砂岩通常都与页岩互层。 来自辞典例句
- Oil-yielding organic matter is contained in the shales. 在这些页岩里有产油的有机物质。 来自辞典例句
- You'll need tweezers to hold up the specimen.你要用镊子来夹这标本。
- This specimen is richly variegated in colour.这件标本上有很多颜色。
- 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》
- Snakes and crocodiles are both reptiles. 蛇和鳄鱼都是爬行动物。 来自《简明英汉词典》
- Birds, reptiles and insects come from eggs. 鸟类、爬虫及昆虫是卵生的。 来自《现代汉英综合大词典》
- Insects and worms are all invertebrates. 昆虫和蠕虫都是无脊椎动物。 来自辞典例句
- In the earthworm and many other invertebrates, these excretory structures are called nephridia. 在蚯蚓和许多其它无脊椎动物中，这些排泄结构称为肾管。 来自辞典例句