Around 520 million years ago, a walking cactus roamed the Earth. Its body had nine segments, each bearing a pair of armour-plated legs, covered in thorns. It was an animal, but one that looked more like the concoction of a bad fantasy artist. Jianni Liu from Northwest University in Xi’an discovered this bundle of spines and named it Diania cactiformis – the “walking cactus from Yunnan”. And she thinks that it sits at the roots of the most successful group of animals on the planet. If Liu is right, Diania is one of the earliest relatives of the arthropods – the group that includes insects, spiders, crabs, and more. These species all share a segmented body, a hard external skeleton and jointed legs. They are life’s winners, the most diverse of all animal groups.