Anomalocaris was a carnivore. It ate Trilobites and the first fish, Haikouichthys. It had a bony crushing plate for a mouth, that couldn't close completely. It also had two spiky appendages that protruded from its head, used to pick up prey, stab them, and lift the food into its mouth. One of its reasons for being such a successful hunter is that it had eyes. Its prey had developed them too, but many creatures didn't have them at the time.
An actual trilobite fossil
Anomalocaris Exoskeleton fossil
Haikouichthys, the thumb sized snack. Perfect choice for wimpy anomalocarises that don't want to chew.