Scientists revealed new research based on a cache of fossils that contains the brain and nervous system of a half-billion-year-old marine predator from the Burgess Shale called Stanleycaris. Stanleycaris belonged to an ancient, extinct offshoot of the arthropod evolutionary tree called Radiodonta, distantly related to modern insects and spiders. These findings shed light on the evolution of the arthropod brain, vision, and head structure.