Discovered in the Ediacara Hills of Australia, Spriggina fossils show what are probably the oldest examples of a head and a tail, having lived 550 million years ago.
Many earlier animals had a circular profile resembling modern anemones and jellyfish, but the body of Spriggina was covered in rugged, plate-like structures.
The first two sections are fused together to formed a 'head' in the shape of a horseshoe. There are a couple of depressions on its upper surface, which may have contained eyes.
The creature has variously been described as a primitive worm, a sort of sea anemone and the ancestor of the trilobites.
Some palaeontologists think that they have found evidence of spines on its head, and believe that it may have been the oldest known predator.
Others argue that it couldn't move at all or that it crawled slowly across the seabed. Much about Spriggina remains a mystery.