【OG24-590题】According to the passage, the anatomical evidence provided by the preserved soft bodies of conodonts led scientists to conclude that_mofa留学圈mofaGRE在线题库系统_GRE在线搜题_GRE题库解析_GRE真题机经_GRE课程_GRE培训机构

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Conodonts, the spiky phosphatic remains (bones and teeth composed of calcium phosphate) of tiny marine animals that probably appeared about 520million 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 there 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, externa! 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 notochord 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 moreprimitive 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.

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

正确答案： D

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文章大意逻辑
牙形石（Conodonts）是小型海洋动物的尖状磷酸盐残骸，曾是最具争议的化石之一，其所属生物的性质和残骸功能未知。1981年发现了不仅保存磷酸盐元素，还保存了软组织的化石，这对脊椎动物骨骼发育假说有重要意义。传统观点认为脊椎动物骨骼是防御性发展，先有骨质鳞片或板，牙齿是次生特征。其他古生物学家则认为第一批脊椎动物是掠食性的，牙齿比外部装甲更原始。 文章类型及逻辑简图
文章类型：新旧观点对比 逻辑简图： Conodonts were controversial fossils, nature and function unknown. 1981 discovery of fossils with soft bodies has implications for vertebrate skeleton hypotheses. Traditional view: vertebrate skeleton as defensive, teeth secondary. Other paleontologists' view: first vertebrates were predatory, teeth more primitive. 做题方法及问题类型
问题类型：细节题 做题方法：根据题干中“the anatomical evidence provided by the preserved soft bodies of conodonts”定位到文章中相关内容。 选项分析
A选项：文中未提及牙形石是无脊椎食肉动物，排除。 B选项：文中没有说牙形石的牙齿由保护性骨质鳞片适应而来，排除。 C选项：文章未表明牙形石是原始脊椎悬浮进食者，排除。 D选项：根据文中对不同观点的阐述，其他古生物学家认为牙齿比外部装甲更原始，意味着有牙齿的原始脊椎动物出现得比有装甲的脊椎动物早，该项正确。 E选项：科学家最初对牙形石磷酸盐残骸的观察是否正确文中未提及，排除。

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