托福考试易错题（2019/3/28）

Ceratopsia
Ceratopsia thrived in NorthAmerica andAsia during theCretaceous 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, butCeratopsians were herbivores¹, so their horns were defensive in nature and may have been used to enforce order in the group. ■
B、Not allCeratopsians had horns, but all had beaklike mouths. ■
C、The fossil record has revealed three distinct families amongCeratopsia: Psittacosaurids, Protoceratopsids, andCeratopsids. Triceratops, a member of theCeratopsid family, is probably the best known species ofCeratopsiA、With its facial horns and neck display, it exhibits many of the features commonly associated with this dinosaur group. ■
D、However, there are species ofCeratopsia 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 inEastAsiA、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 earlyCeratopsians, 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 theCeratopsians.
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 theCeratopsids on the whole, they were still relatively small and hornless. Protoceratops, a six-foot-long quadrupedal herbivore, is a representative ProtoceratopsiD、Fossil examples found inChina and Mongolia show that it had a turtle-like beak and a neck frill, a version of which would show up among the more familiarCeratopsids. While Protoceratops did have some knobby points on its skull, the points only slightly hinted at the impressive horns that appeared on theCeratopsids.
With the arrival of Triceratops and other advancedCeratopsids,Ceratopsia reached new levels of sophistication, variety, and size.AllCeratopsid fossils have been found in western NorthAmerica 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. MostCeratopsids had two long brow horns and a short horn on the nasal ridge.Because theCeratopsids 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 ofCeratopsian species that do not neatly fall into the familial categories as describeD、While these species appear closely related toCeratopsia, they tend to be

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