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  3. Ceratopsia Ceratopsia thrived in North America and Asia

Ceratopsia Ceratopsia thrived in North America and Asia

游客2024-01-04  25
问题                     Ceratopsia
    Ceratopsia thrived in North America and Asia during the Cretaceous Period (about 146 to 65.5 million years ago). Their name means "horned face" and indeed many of them did feature bony horns projecting from their skulls.
(A) The horns may look quite predatory, but Ceratopsians were herbivores1, so their horns were defensive in nature and may have been used to enforce order in the group.
(B) Not all Ceratopsians had horns, but all had beaklike mouths.
(C) The fossil record has revealed three distinct families among Ceratopsia: Psittacosaurids, Protoceratopsids, and Ceratopsids. Triceratops, a member of the Ceratopsid family, is probably the best known species of Ceratopsia. With its facial horns and neck display, it exhibits many of the features commonly associated with this dinosaur group.
(D) However, there are species of Ceratopsia that are quite different from the familiar Triceratops.
    The Psittacosaurids comprise the Psittacosaurus genus2 and the Hongshanosaurus genus. Although not much fossil data are available for Hongshanosaurus, comparisons with Psittacosaurus can be made. Evidence indicates that both were roughly deer-sized bipeds dwelling in East Asia. Hongshanosaurus had beak points on both upper and lower jaws, while only the upper jaw of Psittacosaurus was pointed. Much more fossil evidence is available for Psittacosaurus species. At least one species had long quills along its back and tail. Researchers speculate these quills were used for display during mating or fighting. As early Ceratopsians, the Psittacosaurids had many anatomical features that would show up in similar or interestingly modified forms in later species, but none of the Psittacosaurids had the neck frills or facial horns that came to be associated with the Ceratopsians.
    Although their name suggests that the Protoceratopsids were the first of this dinosaur group to have horned faces, they, in fact, lacked the well-developed horns of later species. While they more closely resembled the Ceratopsids on the whole, they were still relatively small and hornless. Protoceratops, a six-foot-long quadrupedal herbivore, is a representative Protoceratopsid. Fossil examples found in China and Mongolia show that it had a turtle-like beak and a neck frill, a version of which would show up among the more familiar Ceratopsids. While Protoceratops did have some knobby points on its skull, the points only slightly hinted at the impressive horns that appeared on the Ceratopsids.
    With the arrival of Triceratops and other advanced Ceratopsids, Ceratopsia reached new levels of sophistication, variety, and size. All Ceratopsid fossils have been found in western North America and reveal that they were quadrupedal herbivores with beaked jaw tips and rows of teeth specialized for shearing. The family featured a remarkable array of horns, neck frills, and spines. These neck frills, manifesting in various shapes and sizes, probably were too thin to be practical as a defense against predator species, and researchers speculate that they were used during mating displays, for anchoring jaw muscles, for regulating body temperature, or for a combination of these purposes. Most Ceratopsids had two long brow horns and a short horn on the nasal ridge. Because the Ceratopsids were vegetarian and fairly large (up to 30 feet long and 10 feet tall), researchers think that the horns, along with the neck frills, largely served functions of competition, whether in displays or combat. Moreover, since intraspecific conflicts often are tests of strength rather than fights to the death, thin neck frills may have been sturdy enough to provide some protection during such confrontations.
    There is evidence of Ceratopsian species that do not neatly fall into the familial categories as described. While these species appear closely related to Ceratopsia, they tend to be smaller and more primitive. Researchers have debated over recognizing a distinctly new Ceratopsian family or grouping these misfit species with an existing family. Psittacosaurids, Protoceratopsids, and Ceratopsids are the commonly accepted Ceratopsian families with established member species and defined characteristics. Despite some controversies over minor species, a view of the Ceratopsian families is a view of fascinating adaptations and development in a unique dinosaur group. [br] In paragraph 5, the author mentions species that do not fit into the described families in order to
选项 A、point out the imperfect classification system that scientists use.
B、direct attention to a new but unnamed family of significant Ceratopsian species.
C、clarify that the described families include most, but not all related species.
D、emphasize the mysterious nature of Ceratopsi
答案 C
解析 判断意图题 这是判断作者意图的问题。第五段提到一些角龙类没有划分到现有的角龙科。本段阐述了科学家们对于如何将这些物种归类的不同意见。作者没有指出现有分类体系不完整。因此，A项是错误答案。而且文章指出不是主要物种(significant)而是少数物种(minor)存在这个问题，文章也没有呼吁对这些物种给予足够的重视，因此B项是错误答案。作者指出之前的分类方式没有将所有的角龙种类包含在内。因此C项是正确答案。
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