白垩纪
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白垩纪；白垩系
n. from 135 million to 63 million years ago; end of the age of reptiles; appearance of modern insects and flowering plants；a. abounding in chalk；a. of or relating to or denoting the third period of the Mesozoic era
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白垩系的；白垩纪的；白垩纪；白垩系
n. from 135 million to 63 million years ago; end of the age of reptiles; appearance of modern insects and flowering plants；a. abounding in chalk；a. of or relating to or denoting the third period of the Mesozoic era
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