章节大纲

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  • 爬动演变

    Three dinosaurs depicted near a water body in a prehistoric landscape.

    So what exactly is a dinosaur?
    ::恐龙到底是什么?

    Dinosaurs were not lizards. Rather, they were a separate group of with a distinct upright posture not found in lizards. Dinosaurs can be described as large, powerful reptiles. And many were very big. But dinosaurs were more than that. They were a varied group of with over 1,000 non-avian .
    ::恐龙不是蜥蜴,相反,它们是一个单独的群体,有着在蜥蜴中找不到的明显的直立姿势。恐龙可以说是大而强大的爬行动物。许多是很大的爬行动物。但恐龙还不止于此。它们是一个由1000多个非禽类组成的不同群体。

    Evolution of Reptiles
    ::爬行的演变

    The earliest amniotes evolved about 350 million years ago. They resembled small lizards, but they were not yet reptiles. Their amniotic eggs allowed them to move away from bodies of and become larger. They soon became the most important land vertebrates .
    ::最早的羊膜动物在大约3.5亿年前就进化了。它们类似于小蜥蜴,但还没有爬行动物。它们的羊蛋允许它们离开身体,长大。 它们很快成为最重要的脊椎动物。

    Synapsids and Sauropsids
    ::合成机和合成机

    By about 320 million years ago, early amniotes had diverged into two groups, called synapsids and sauropsids . Synapsids were amniotes that eventually gave rise to mammals . Sauropsids were amniotes that evolved into reptiles, dinosaurs, and . The two groups of amniotes differed in their skulls. The earliest known reptile, pictured in Figure , dates back about 315 million years.
    ::大约在3.2亿年前,早期的羊水分化成两组,称为突触和沙罗皮斯。合成物是羊水,最终导致哺乳动物的产生。黄鼠狼是羊水,演变成爬行动物、恐龙和。两组羊头骨不同。最早已知的爬行动物,如图所示,可追溯到大约3.15亿年前。

    Reconstruction of Hylonomus, the earliest known reptile, featuring distinct coloration and posture.
    Earliest Reptile: Hylonomus. The earliest known reptile is given the genus name Hylonomus. It was about 20 to 30 centimeters (8 to 12 inches) long, lived in swamps, and ate insects and other small invertebrates.

    At first, synapsids were more successful than sauropsids. They became the most common vertebrates on land. However, during the Permian 245 million years ago, most synapsids went extinct. Their niches were taken over by sauropsids, which had been relatively unimportant until then. This is called the Triassic takeover .
    ::起初,突触比沙罗普西德更成功,成为陆地上最常见的脊椎动物。然而,在波尔米亚2.45亿年前,大多数突触动物灭绝了。它们的位置被沙罗普西德人所占据,而在那之前这些地方相对无关紧要。这被称为三亚西克人接管。

    Rise and Fall of the Dinosaurs
    ::恐龙的起落

    By the middle of the Triassic about 225 million years ago, sauropsids had evolved into dinosaurs . Dinosaurs became increasingly important throughout the rest of the , as they radiated to fill most niches. This is why the Mesozoic Era is called the Age of the Dinosaurs . During the next mass extinction, which occurred at the end of the Mesozoic Era, all of the dinosaurs went extinct. Many other reptiles survived, however, and they eventually gave rise to modern reptiles.
    ::在大约2亿2千5百万年前的三千五百万年前的三千五百万年前,沙罗普西德已经演变成恐龙。在其余部分,恐龙变得日益重要,因为它们在辐射以填满大部分空隙。这就是为什么梅索佐伊克时代被称为恐龙时代。在下一次大规模灭绝(发生在中索索伊克时代末期)期间,所有恐龙都灭绝了。然而,许多其他爬行动物生存下来,最终产生了现代爬行动物。

    Evolution of Modern Reptile Orders
    ::现代定居令的演变

    Figure shows a traditional phylogenetic tree of living reptiles. Based on this tree, some of the earliest reptiles to diverge were ancestors of . The first turtle-like reptiles are thought to have evolved about 250 million years ago. Ancestral crocodilians evolved at least 220 million years ago. Tuataras may have diverged from squamates (snakes and lizards) not long after that. Finally, went their separate ways about 150 million years ago.
    ::图中显示了一种传统的活爬行动物的植物基因树。根据这棵树,一些最早分裂的爬行动物是它的祖先。第一种象龟一样的爬行动物被认为在2.5亿年前就已经进化了。至少2.2亿年前就已经进化了。图阿塔拉可能在那之后不久就脱离了同族动物(鼻和蜥蜴 ) 。最后,在大约1.5亿年前,他们又采取了不同的方法。

    Traditional phylogenetic tree illustrating the evolution of modern reptile orders.
    Traditional Reptile Phylogenetic Tree. This phylogenetic tree is based on physical traits of living and fossil reptiles. Trees based on DNA comparisons may differ from the traditional tree and from each other, depending on the DNA sequences used. Reptile evolution is currently an area of intense research and constant revision.

      

     

     

     

    Summary
    ::摘要

    • The earliest amniotes appeared about 350 million years ago, and the earliest reptiles evolved from a sauropsida ancestor by about 315 million years ago.
      ::最早的羊膜在大约3.5亿年前出现,最早的爬行动物从沙罗普西达祖先演变为大约3.15亿年前。
    • Dinosaurs evolved around 225 million years ago and dominated animal life on land until 65 million years ago, when they all went extinct.
      ::恐龙在大约2亿2千5百万年前形成 陆地上以动物为主 直到6500万年前 它们都灭绝了
    • Other reptiles survived and evolved into the classes of reptiles that exist today.
      ::其他爬行动物幸存下来,演变成今天存在的爬行动物类别。

    Review
    ::回顾

    1. Identify amniotes called synapsids and sauropsids.
      ::识别被称作突触和索罗皮斯的羊膜
    2. Give a brief overview of reptile evolution.
      ::简要概述爬行动物的演变。
    3. Explain why reptiles were able to replace amphibians as the dominant land vertebrates.
      ::解释爬行动物为什么能够取代两栖动物,成为占支配地位的陆脊椎动物。