Diania cactiformis is a 520 million year old organism with 20 legs, and possibly the closest relative to arthropods. Its body is soft, while its legs are hard and covered in spines. Though it doesn’t appear to have eyes, a mouth, or a head, it does have jointed legs.

http://blogs.discovermagazine.com/notrocketscience/2011/02/23/meet-diania-the-walking-cactus-an-early-cousin-of-lifes-great-winners/