Opabinia was a strange Cambrian arthropod with five eyes, a v-shaped tail, and a long stalk, with jaws and a mouth under its head. It used its long appendage to grab prey. Then it would shove the prey into its circular mouth. The name is pronounced oh-puh-BIN-ee-uh.
Opabinia probably hunted in worm burrows by sticking its long appendage into the burrow, and then pulling out the worm inside. If there was a worm in that burrow. Opabinia was about 3" long.
Opabinia had predators, like Anomalocaris and Sanctacaris. It hunted on the sea floor.