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
2018-05-07
78
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
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://www.kaotiyun.com/show/GX8R777K
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
根据信息系统与企业组织之间的关联关系,可以将信息系统分为多个系统类别,在这些类别中整合了多个部门的流程,实现了整个组织信息的自动化采集和传递的是()
劳动力商品使用价值的重要特点是,随着其使用价值的消费()
Americansareaveryenergeticandmobilepeople,alwaysontherun,rushingfromoneappointmenttoanother,fromaPTA(Parent-Tea
Curiosityisnotonlyapossiblemotivation,itisalsoagreathelpinyourlearninglanguages.Rememberthatalanguageisnot
Thebasicprincipleofradarisillustratedbywhathappenswhenoneshoutsinacave.Theechooftheshouting(11)______the
Generallyspeaking,thequalityoflife,especiallyas______(see)bytheindividual,ismeaningfulintermsofthedegreetowhic
Afewyearsagoitwasfashionabletospeakofagenerationgap,adivisionbetweenyoungpeopleandtheirelders.Parentscompla
A.borntobemoreintelligentorlessintelligentB.haveabetterchancetodevelophisintelligenceC.can’tbeobservedand
HowLongCanaHumanSurviveWithoutWaterandFood?Peopledonotneedfoodasmuchastheydowater.Infact,theycansur
RareFossilRecordThepreservationofembryosandjuvenilesisarareoccurrenceinthefossilrecord.Thetiny,delicates
随机试题
钨极氩弧焊在大电流区间焊接时,其静特性为下降特性区。
抑郁发作的核心症状不包括【】
强夯法的单位夯击能量,应根据荷载大小和()等综合考虑,可通过现场试夯确定,一般情况下对砂性土取1000~5000kN.m/m2,黏性土可取1500~6000kN.m/m2。
影响建筑结构耐火性能的因素有()。
下列各项中,不符合票据和结算凭证填写要求的是()。
我国迄今发现的最早瓷器是在()。
为了尽快击败德国,苏联、美国和英国三国政府首脑在()上最后确定从法国北部登陆,开辟第二战场。
欢天喜地:兴高采烈
现代人对微信__________不已。乃至几乎不能有一朝一夕的分离,与其说是微信的功能强大,不如将之理解成空虚寂寞冷的人们,需要某种精神层面的__________。依次填入划横线部分最恰当的一项是:
Itwouldhavebeen______impossibletoresearchalltheinformationonthistopic.
最新回复
(
0
)