Around 530 million years ago, the planet teemed with life after the Cambrian explosion, when most major animal groups we see today started to appear in the fossil record. Most of this abundance was concentrated in the oceans, which were rich with fantastical creatures such as armored trilobites, three-foot-long shrimp, and worms bristling with vicious spikes.
But fossil records show that just 20 years later, something decimated 45% of all animals in the ocean. This major extinction event delivered destruction on an unprecedented scale.
