地球在她45亿年的历史长河中，已经见证了几次大规模的灭绝，但是发生在二叠纪末的整个重大事件在规模上堪称史无前例。
The Earth has witnessed several mass extinctions in its 4.5bn year history, but the event that struck at the end of the Permian was unequaled in scale.
地球在她45亿年的历史长河中，已经见证了几次大规模的灭绝，但是发生在二叠纪末的整个重大事件在规模上堪称史无前例。
The Earth has witnessed several mass extinctions in its 4.5bn year history, but the event that struck at the end of the Permian was unequaled in scale.
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