短语词组短語mid late proterozoic era 中晚元古代Early Late Proterozoic Era 晚元古代早期mid -proterozoic era 中元古界early proterozoic era 早元古代Middle Proterozoic era 中元古界Lower Proterozoic Era 下元古middle -upper proterozoic era 中上元古界 返回 proterozoic era