Ordovician:
The Ordovician /ɔrdəˈvɪʃən/ is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between Ordovician and Silurian million years ago ICS 2004. It follows the Cambrian period and is followed by the Silurian period.
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奥陶纪:
奥陶纪（Ordovician，符号O）是地质时代中显生宙古生代的第二个纪，约开始于4.9亿年前，结束于4.38亿年前。
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Ordovician奥陶纪