Ancient Oceans - Episode Guide

For nearly 4 billion years, the continents of Earth were a lifeless wasteland. But beneath the sea, our planet was teeming with life. Many strange creatures evolved, from eel-like conodonts to voracious cephalopods, until nearly all life was wiped out in our planet's first mass extinction.

Life in the sea rebounded with a vengeance in the Devonian. Dozens of monstrous predators emerged, like the 40-foot long Dunkleosteus. Nearly everything was wiped out in Earth's second mass extinction. But the stage was set for an explosion of life on land.