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
Kare Fossil Record The preservation of embryos and juveniles is a rare occurrence in the fossil record.The tiny, delicate sk
Kare Fossil Record The preservation of embryos and juveniles is a rare occurrence in the fossil record.The tiny, delicate sk
admin
2021-01-25
30
问题
Kare 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 early 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 ale well preserved.
C、To indicate how the ichthyosaurs died.
D、To prove that ichthyosaurs are marine animals.
答案
A
解析
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://jikaoti.com/ti/hlAfFFFM
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
马克思根据人的发展状况,把人类历史划分为依次更替的三大社会形态。属于这三大社会形态的有_______、_______、_______。
Americansareaveryenergeticandmobilepeople,alwaysontherun,rushingfromoneappointmenttoanother,fromaPTA(Parent-Tea
Curiosityisnotonlyapossiblemotivation,itisalsoagreathelpinyourlearninglanguages.Rememberthatalanguageisnot
Britainhasthousandsofroad______(fatal)everyyear.
IncomeIncomemaybenationalincomeandpersonalincome.Whereasnationalincomeisdefinedasthetotalearnedincomeofa
TheOperationofInternationalAirlinesInternationalairlineshaverediscoveredthebusinesstraveler,themanorwomanwho
LegalProtectionIndividualsandbusinesseshavelegalprotectionforintellectualpropertytheycreateandown.Intellectua
SavingMoneyWhereyousaveyourmoneyoftendependsonwhatyouaresavingfor.Ifyouaresavingtobuyadictionaryorto
TheWorkers’RoleinManagementTraditionally,ithasbeentheworkers’roletoworkandmanagement’sroletomanage.Manage
KareFossilRecordThepreservationofembryosandjuvenilesisarareoccurrenceinthefossilrecord.Thetiny,delicatesk
随机试题
治疗气滞痰郁所致郁证的最佳方剂是()(2007年第53题)
卡斯特等人的管理理论被人们称为【】
所有T细胞都具有的标志性抗原是
钻芯芯样试件宜在与被检测结构或构件混凝土湿度基本一致的条件下进行抗压试验。()
从信息管理组织角度,可以将工程造价信息分为()。
甲乙公司均为一般纳税人,适用的增值税税率为17%。2013年3月2日,甲公司向乙公司赊销商品一批,商品标价总额为200万元(不含增值税)。由于成批销售,乙公司应享受10%的商业折扣,销售合同规定的现金折扣条件为2/10,1/20,n/30。假定计算现金折
根据以下资料,回答下面小题。下列说法与资料不相符的是()。
斯大林模式形成的标志()。
(1997年试题,九)从学校乘汽车到火车站的途中有3个交通岗,假设在各个交通岗遇到红灯的事件是相互独立的,并且概率都是.没X为途中遇到红灯的次数,求随机变最X的分布律、分布函数和数学期望.
下列哪个命令用于保存来自Cisco控制器CLI的配置?A、wremB、copyrunstartC、saveconfigD、Save
最新回复
(
0
)