Palaeontologists at the Manitoba Museum and Royal Ontario Museum (ROM) have discovered a remarkable new 506-million-year-old predator from the Burgess Shale of Canada. Mosura fentoni was about the size of your index finger and had three eyes, spiny jointed claws, a circular mouth lined with teeth and a body with swimming flaps along its sides. These traits show it to be part of an extinct group known as the radiodonts.