The Cambrian predator with multiple appendages and a circular mouth was Anomalocaris. Its name means “unlike other shrimp,” reflecting an early misinterpretation of its fossil fragments.
Anomalocaris lived roughly 500 million years ago and is best known from the Burgess Shale in British Columbia. It had large compound eyes, a pair of grasping frontal appendages, rows of swimming flaps, and a tail fan. Its disk-shaped mouth, called an oral cone, was made of several tooth-like plates arranged around a central opening.
Because of its size, speed, sensory equipment, and grasping limbs, Anomalocaris is considered one of the earliest apex predators. Earlier reconstructions portrayed it as capable of crushing trilobites, but newer studies suggest its appendages were better suited to catching soft-bodied, free-swimming prey. Fossil evidence also shows that related radiodonts occupied several different feeding roles.
Pikaia was a chordate, Hallucigenia was a spiny worm-like animal, and Opabinia had five eyes and a single flexible proboscis. None had Anomalocaris’s distinctive combination of frontal limbs and circular oral cone.