Opabinia is an evolutionary dead end, since no currently existing species is related to it, and today its classification is still discussed. It had five functional eyes and only one appendage, sticking out of its head. Supposedly, it used it to look for worms in floor sediments and bring the food to its mouth, like today’s elephants.
See it in action and get more info
Artist representations make it look like an E.T. escaped from a 50’s pulp. *shudders*