Ordovician

【地质】奥陶纪; 奥陶系; [the Ordovician ]奥陶时期; 奥陶纪层

Ordovician

of, denoting, or formed in the second period of the Palaeozoic era, between the Cambrian and Silurian periods, which lasted for 45 000 000 years during which marine invertebrates flourished