With help from 15 fossils recently discovered in Greenland, scientists are now able to peer inside the brain of an animal that lived 520 million years ago.

The extinct species, Kerygmachela kierkegaardi, swam in ocean waters during an evolutionary arms race called the Cambrian explosion. Flanked by 11 wrinkly flaps on each side of its body, the ancient predator sported a long tail spine and a rounded head. Its fearsome forward-facing appendages grasped prey, says UK-based paleontologist Jakob Vinther, “making lives miserable for other animals.”

Previous fossil remains of the roughly one- to ten-inch creature came from loose rocks battered by weather. But the new finds are the species' first to escape exposure to the elements, resulting in fossil