Conodonts, the spiky phosphatic remains(bones and teeth composed of calcium phosphate) of tiny marine animals that probably appeared about 520 million years ago, were once among the most controversial of fossils. Both the nature of the organism to which the remains belonged and the function of the remains were unknown. However, since the 1981 discovery of fossils preserving not just the phosphatic elements but also other remains of the tiny soft-bodied animals (also called conodonts) that bore them,scientists' reconstructions of the animals' anatomy have had important implications for hypotheses concerning the development of the vertebrate skeleton.
The vertebrate skeleton had traditionally been regarded as a defensive development, champions of this view postulating that it was only with the much later evolution of jaws that vertebrates became predators. The first vertebrates, which were soft-bodied, would have been easy prey for numerous invertebrate carnivores, especially if these early vertebrates were sedentary suspension feeders. Thus, traditionalists argued,these animals developed coverings of bony scales or plates, and teeth were secondary features, adapted from the protective bony scales. Indeed, external skeletons of this type are common among the well-known fossils of ostracoderms, jawless vertebrates that existed from approximately 500 to 400 million years ago. However, other paleontologists argued that many of the definitive characteristics of vertebrates, such as paired eyes and muscular and skeletal adaptations for active life, would not have evolved unless the first vertebrates were predatory. Teeth were more primitive than external armor according to this view, and the earliest vertebrates were predators.
The stiffening not ochord along the back of the body, V-shaped muscle blocks along the sides, and posterior tail fins help to identify conodonts as among the most primitive of vertebrates. The lack of any mineralized structures apart from the elements in the mouth indicates that conodonts were more primitive than the armored jawless fishes such as the ostracoderms. It now appears that the hard parts that first evolved in the mouth of an animal improved its efficiency as a predator, and that aggression rather than protection was the driving force behind the origin of the vertebrate skeleton.

第1题 第2题 第3题

According to the passage, the anatomical evidence provided by the preserved soft bodies of conodonts led scientists to conclude that


conodonts had actually been invertebrate carnivores

conodonts' teeth were adapted from protective bony scales

conodonts were primitive vertebrate suspension feeders

primitive vertebrates with teeth appeared earlier than armored vertebrates

scientists' original observations concerning the phosphatic remains of conodonts were essentially correct

加入错题本 分享
纠错
考题讲解

文章大意：

1. Conodonts，最有争议的化石：本质、功能全不知。

However，1981的新发现可以帮助科学家研究脊椎动物骨骼的发展。

2. 脊椎动物的骨骼一度被认为是用来防御的；有下巴才是捕食者的特征；举例，甲青鱼，500到400百万年前出现的没下巴的脊椎动物。

However，其他学者认为一代脊椎动物有符合捕食者的特征。

3. C是比甲青鱼（ostracoderms）更原始。

题目分析：

文章推断题：C的软骨可以帮助科学家得出什么结论？

选项分析：

A选项：C其实是无脊椎的食肉动物：文章明确表示C是脊椎动物。

B选项：C的牙齿是从保护性的骨鳞发展来的：这个观点是有争议的，而根据第三段，这个观点是被削弱的。

C选项：C是原始的有脊椎的悬浮物摄食者：文章最后一句说明C是predator而不是悬浮物摄食者。

D选项：正确。有牙的原始脊椎动物比有甲的脊椎动物出现的早：第三段支持了这个观点。

E选项：科学家对最早的关于含磷酸盐的C的残骸的观察是准确的：科学家最早认为C不是predator，而后面反驳了这个观点，说明早期的观察是不准确的。

展开显示

登录 或 注册 后可以参加讨论

OG2019-RC