白垩系的
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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
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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