The Palaeozoic has been broken down into six smaller units of geological time called periods. Cambrian is the oldest period of the Palaeozoic followed successively by Ordovician, Silurian, Devonian, Carboniferous and Permian Periods.

• 古生代可划分成6个小的叫做纪的时间单位，寒武纪是古生代中最老的一个纪，然后依次为奥陶纪、志留纪、泥盆纪、石炭纪和二叠纪。