像三叶虫和腕足类一样的贝壳类生物是谁的祖先在岩石中得到一点提示，这些东西到处都是。
Shelly creatures such as trilobites and brachiopods, of whose ancestors there is little sign in the rocks, are suddenly everywhere.
像三叶虫和腕足类一样的贝壳类生物是谁的祖先在岩石中得到一点提示，这些东西到处都是。
Shelly creatures such as trilobites and brachiopods, of whose ancestors there is little sign in the rocks, are suddenly everywhere.
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