久久99热精品,久久国产精品久久,久久人人国产,国产精品久久久久久久久久嫩草,欧美伦理电影免费观看,国产女教师精品久久av,精品国产乱码久久久久久虫虫

高中英語作文:罕見的化石記錄(Rare fossil record)

時間:2022-08-05 20:46:55 其他類英語作文 我要投稿

高中英語作文:罕見的化石記錄(Rare fossil record)

  在日常學(xué)習(xí)、工作抑或是生活中,說到作文,大家肯定都不陌生吧,借助作文人們可以反映客觀事物、表達思想感情、傳遞知識信息。作文的.注意事項有許多,你確定會寫嗎?以下是小編幫大家整理的高中英語作文:罕見的化石記錄(Rare fossil record),歡迎閱讀與收藏。

高中英語作文:罕見的化石記錄(Rare fossil record)

  the preservation of embryos and juveniles is a rate occurrence in the fossil record. the tiny, delicate skeletons are usually scattered 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 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 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 eample, 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.

【高中英語作文:罕見的化石記錄(Rare fossil record)】相關(guān)文章:

Protect Rare Animals英語作文范文08-17

罕見的日全食作文07-31

罕見的日全食08-16

罕見的秋雨作文300字03-21

小學(xué)作文:罕見的日全食08-29

I must record this week_250字09-18

保護珍稀動物英語作文Protect Rare Animals01-30

保護珍稀動物英語作文Protect Rare Animals04-23

罕見的日全食作文4篇10-13

东乌珠穆沁旗| 梁河县| 镇江市| 涟源市| 甘泉县| 广灵县| 公安县| 特克斯县| 库伦旗| 华蓥市| 南和县| 娄底市| 德安县| 高要市| 柳江县| 禹州市| 禄丰县| 娄烦县| 贺兰县| 广宁县| 宾川县| 拜城县| 民县| 娄烦县| 巴彦淖尔市| 宝坻区| 肇庆市| 穆棱市| 白河县| 和政县| 建德市| 泰来县| 巨野县| 弥勒县| 怀化市| 大关县| 平凉市| 枣庄市| 永安市| 陈巴尔虎旗| 泗洪县|