and Dunkleosteus had reigned for 20 million years. 邓氏鱼已经统治了2000万年
It's a hunting technique that has been honed over millions of years. 这是一种经过数百万年 得以完善的捕猎技巧
They first appeared more than 400 million years ago 它们最早出现在四亿多年前
Seventy million years after the great melt, 大融化7000万年之后
200,000 years after the big freeze, 大冰冻的20年之后
It first evolved hundreds of millions of years ago, 最早在数亿年前进化
One that would last for 200,000 years. 这个时期将持续20万年
Twenty million years later, life faced one of its greatest challenges... 2000万年后 生命面临又一个巨大的挑战
Forty million years later, and a new era of life has begun, 四千万年后 一个新的生命纪♥元♥开始
And in the tropical shallows 508 million years ago, 在5.08亿年前的热带浅海中