For the inhabitants of Earth's once tropical waters, 过去地球上热带水域的“居民们”
...as the climate suddenly began to cool... 气候突然变冷
But for now, vertebrates are only at the beginning 但是现在脊椎动物仍处于
But what it has evolved will change the course of history. 但它进化出的特征将改变历史进程
...able to slice through the toughest armor, 能够切割最硬的护甲
All the trilobite can do is try to stay out of reach. 三叶虫能做的只有设法保持距离
The trilobite is dwarfed by this towering hunter. 三叶虫在这高耸的猎手面前相信见拙
are part of a dynasty known as the cephalopods. 它们属于头足动物这个新王朝
The largest, with a shell eight meters long, 最大的 壳长八米