Anomalocaris ('unlike other shrimp' or 'abnormal shrimp') was a member of the radiodont order of arthropods and is thought to be one of the earliest known apex predators. It was quite large for its time, up to 38 cm (1.25 ft) in body length and another 18cm (7 inches) added by its frontal appendages. It moved by waving the flaps on the side of its body.
(Cambrian, ~540 million years ago)