斯大林格勒大战>蒜茸油麦菜rare fossil record阅读理解答案
钠摄入过多会怎样The prervation 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 prerved than did terrestrial creatures becau, 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 the factors, some areas have become a treasury of well-prerved ichthyosaur fossils.德开头的成语
胚胎与幼体被保存下来在化石记录中是少见的事情。微小纤细的骨骼通常在石化前就被食腐肉的动物拆散了，或者被风化作用破坏掉了。鱼龙比起陆地的动物有更大的几率被保存下来，因为它们作为海洋动物常生活在腐蚀性较小的环境中。但是它们的石化需要一系列因素：软组织的腐烂速度缓慢，很少被其他动物残食，缺少混杂、冲走小骨头的快速水流和波浪，以及相当快地被掩埋。当这些因素存在时，某些地区就会变成一个充满保存完好的鱼龙化石的宝库。
狐狸头饰
霍启刚个人资料简介 The deposits at Holzmaden, Germany, prent an interesting ca 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 the rocks. The quality of prervation is outstanding, but what is even more impressive is the number of ichthyosaur fossils containing prerved 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 ud 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 prerved in the birth canal. In addition, the shale contains the remains of many newborns that are between 20 and 30 inches long.
运算放大器的作用 在德国获尔兹梅登，那儿的沉积物给人们提出了一个有趣的分析案例。人们在黑色的、含沥青的海洋页岩中发现了约19，000年前沉积下来的鱼龙化石。几年时间内，在这些岩石中取得了数以千计的海洋爬行动物、鱼类以及无脊椎动物的标本。它们的保存质量非常的
好，但更令人称奇的是保存下来的育有胚胎的鱼龙化石数目。在获尔兹梅登附近一个小地区的六个不同的页岩层中分别发现了育有胚胎的鱼龙化石。这表明大量的鱼龙经年累月重复使用一个特定的地点。那些胚胎已经发育得相当完整了。比如，它们的蹼桨已经完全形成了。有一个标本甚至被保存在产道中。而且，那块页岩包含着很多在20到30英寸之间的新生幼体的化石。
给好朋友的留言
Why are there so many pregnant females and young at Holzmaden when they are so rare elwhere? The quality of prervation is almost unmatched and quarry operations have been carried out carefully with an awareness of the value of the fossils. But the 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 clo to their time of giving birth.
