A color reconstruction of Hallucigenia. (Credit: Danielle Dufault) If you think this ancient, spiky creature is bizarre, you’re not alone: For years, scientists have struggled to figure out exactly what it is, or was — until now. Scientists recently unearthed spectacular fossil remains of Hallucigenia sparsa, a fierce-looking worm species that lived 508 million years ago. The fossils helped paint the most detailed picture to date of Hallucigenia, yielding important insights into the evolution of modern-day arthropods like insects and arachnids.