You are in the oceans of Australia, 468 million years ago.

The water was warm and shallow, illuminated by a sun that shone down on an alien world—the Ordovician period. You hovered—in your specialized diving gear to withstand the current hostile atmosphere—over a seabed covered in colorful sponges, as you witness an Endoceras—the biggest predator of its time—settling down to munch on a trilobite that it had ensnared with its tentacles. The predatory cephalopod feasts as it rips apart the trilobite’s armor with its crushing beak. Bits of nutrient-rich tissue of the trilobite drift away from the tentacles.

Just then, a tiny movement catches your eye.

A small creature, barely 15 centimeters long, darts out from its hiding spot behind a large sponge. It was an Arandaspis, one of the very first vertebrates. Its body, covered in armored bony scales, moved with a quick, erratic, tadpole-like motion, steering with its long tail rather than fins. The creature seemed timid and inquisitive, its eyes fixed in a look of permanent surprise on its bony, shielded head. And yet you watched it edge closer to the Endoceras, showing no fear of the monster that could swallow it whole.

It was not alone. You soon spotted a few more Arandaspis swimming out of shadows of the sponges. They all hovered only inches from the Endoceras’ beak, each of their jawless, slit-like mouth quickly sucking up the floating scraps of meat, scavengers capitalizing on the efforts of a master predator.

The giant cephalopod, indifferent to the small fish, continued its feast, ignoring the nimble thieves in favor of the massive meal in its clutches, much to your amusement as you continue to observe the feeding frenzy.