A Treasure Trove of Cambrian Fossils Rewrites the Story of Early Life

Roughly 540 million years ago, toward the start of the Cambrian Period, the planet was mostly ocean, and life was both alien and vaguely familiar. Small, phallic-looking worms rummaged through ocean-floor sediments while blind swimming beasts flung out whiplike tentacles to ensnare prey. Meanwhile, early versions of mollusks and sponges populated the seafloor as jellyfish floated above.

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