Designation, or pertaining to, the era during which it was once supposed the earliest forms of life existed.

【地】古生代的。

The geological era just before the Mesozoic, or Age of Reptiles.

古生代。距今约五亿七千万─两亿四千万年前称古生代，在中生代(Mesozoic)之前。古生代分为寒武纪(Cambrian)、奥陶纪(Ordovician)、志留纪(Silurian)、泥盆纪(Devonian)、石炭纪(Carboniferous)、二叠纪(Dermian)。