首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
自考
Rare Fossil Record The preservation of embryos and juveniles is a rare occurrence in the fossil record. The tiny, delicate s
Rare Fossil Record The preservation of embryos and juveniles is a rare occurrence in the fossil record. The tiny, delicate s
admin
2017-04-24
26
问题
Rare Fossil Record
The preservation of embryos and juveniles is a rare occurrence in the fossil record. The tiny, delicate skeletons are usually scattered by scavengers (食腐动物)weathering before they can be fossilized. Ichthyosaurs (鱼龙) 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 (页岩) 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.
Which of the following is true of the fossil deposits discussed in the passage?
选项
A、They include examples of newly discovered species.
B、They contain large numbers of well-preserved specimens.
C、They are older than fossils found in other places.
D、They have been analyzed more carefully than other fossils.
答案
B
解析
推理判断题。由第二、三段可以看出,该地发现的化石的特别之处在于数量之多、保存完好。因此B是最佳选择。其余的选项:并不是发现了新物种,因此排除A;文中未提到其年代比其他地方的久远,因此C不正确;文中没有提及它们比其他的化石更仔细地被研究,D选项也不对。
转载请注明原文地址:https://kaotiyun.com/show/Qm8R777K
本试题收录于:
英语(二)题库公共课分类
0
英语(二)
公共课
相关试题推荐
以下不属于MIS报表的内容的是()
信息系统的开发建设方式不包括()
简述开发方式的优缺点。
在对外经济侵略中,最具新殖民主义特点的做法是()
资本主义的发展史上殖民地对资本主义国家的发展起到的作用是()
在对外经济侵略中,新殖民主义不同于老殖民主义的手法是()
垄断资本主义国家用多种手法剥削和控制发展中国家,其中典型的新殖民主义手法是()
Weallknowthathumansaredamagingtheenvironment,butwhatcanwedoaboutit?Somepeoplearetryingtodotheirbittobemo
Howoftenonehearschildrenwishingtheyweregrownup,andoldpeoplewishingtheywereyoungagain.Eachagehasitspleasures
RareFossilRecordThepreservationofembryosandjuvenilesisarareoccurrenceinthefossilrecord.Thetiny,delicates
随机试题
某县公安局于2012年5月25日以方某涉嫌合同诈骗罪将其刑事拘留,同年6月26日取保候审,8月11日检察院决定批准逮捕方某。2013年5月11日,法院以指控依据不足为由判决方某无罪,方某被释放。2014年3月2日方某申请国家赔偿。下列哪一说法是正确的?
某煤矿发生瓦斯爆炸事故,造成6人死亡,3人受伤,属()
下列文件资料中,属于建设工程监理文件资料的有()。
《中华人民共和国反洗钱法》规定,海关发现个人出入境携带的()超过规定金额的,应当及时向中国人民银行通报。
同业拆借是银行间的短期行为,不能反映金融市场上的资金供求状况。()
下列选项中不属于直接融资工具的是()。
李某因为缴纳税款数额的问题和税务机关发生争议,依据我国《行政复议法》和《行政诉讼法》的规定,李某可以寻求的解决途径是()。
Wheredoesthisconversationtakeplace?
Thetopoftheworldisawonderland.Inwinter,thetemperatureoftenfallsto-30°Fandthesunneverrises.Theoceanissurr
ThemancommittedallthefollowingcrimesEXCEPT_________.
最新回复
(
0
)