Cambrian: the beginning of the Paleozoic Era Animals with hard-shells appeared in great numbers for the first time during the Cambrian.
Cambrian: the beginning of the Paleozoic Era Animals with hard-shells appeared in great numbers for the first time during the Cambrian.
寒武纪：古生代的开始（距今5亿1,400万年前），具有硬壳的生物在寒武纪第一次大量出现。