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
2022-01-21
59
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.
Why does the author mention the specimen preserved in the birth canal?
选项
A、To illustrate that the embryo fossils are quite advanced in their development.
B、To explain why the fossils are well preserved.
C、To indicate how the ichthyosaurs died.
D、To prove that ichthyosaurs are marine animals.
答案
A
解析
推理判断题。第三段中提到保存在产道中的标本。是为了说明胚胎发育的程度很高。因此选A。
转载请注明原文地址:https://kaotiyun.com/show/s08R777K
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
RareFossilRecordThepreservationofembryosandjuvenilesisarareoccurrenceinthefossilrecord.Thetiny,delicates
RareFossilRecordThepreservationofembryosandjuvenilesisarareoccurrenceinthefossilrecord.Thetiny,delicates
RareFossilRecordThepreservationofembryosandjuvenilesisarareoccurrenceinthefossilrecord.Thetiny,delicates
RareFossilRecordThepreservationofembryosandjuvenilesisarareoccurrenceinthefossilrecord.Thetiny,delicates
KareFossilRecordThepreservationofembryosandjuvenilesisarareoccurrenceinthefossilrecord.Thetiny,delicatesk
KareFossilRecordThepreservationofembryosandjuvenilesisarareoccurrenceinthefossilrecord.Thetiny,delicatesk
KareFossilRecordThepreservationofembryosandjuvenilesisarareoccurrenceinthefossilrecord.Thetiny,delicatesk
RareFossilRecordThepreservationofembryosandjuvenilesisarareoccurrenceinthefossilrecord.Thetiny,delicates
随机试题
对白喉的人工主动免疫用________,人工被动免疫用________。
以热力学定律为基础的能量金字塔反映了生态系统内___________流动的规律。
药物引起的接触性口炎多发生在接触药物后
欧阳一家侨居英国,因其在家乡的祖房不愿出售,便托付邻居丁某代为照看。后丁某未经欧阳同意便将其房屋租给来本地经商的人居住,获得1年的预付租金1万元。丁某即用这笔钱投资建了一个快餐馆,1年时间盈利2万元,其中5千元为丁某的劳务管理费用成本。1年后欧阳返乡,发现
无效合同从()时起就不具有法律效力。
公开发行的可转换公司债券,如果存在()的情况,应当召开债券持有人会议。
()是判断贷款正常与否的最基本标志。
2008年政府出台“限塑令”,但现在“限塑令”落实效果并不理想,超市仍在贩卖塑料袋。而且很多外卖、快递等行业也带动了塑料袋的使用。针对“限塑令”所处的困境。请谈谈你的看法。
PassageOneMyclassatHarvardBusinessSchoolhelpsstudentsunderstandwhatgoodmanagementtheoryisandhowitisbuilt
A、Privacy.B、Thelowerprice.C、Money-saving.D、Coupongoods.A短文中提到Inordertosavemoneywiththecards,peoplecouldlosepriv
最新回复
(
0
)