When British palaeontologist Simon Conway Morris first set eyes on a fossil of the creature above in the 1970s, he thought he was hallucinating and so called it Hallucigenia – or to give it its full title, Hallucigenia sparsa.
He, and scientists ever since, have not been able to make head nor tail of the animal – literally they didn’t know which end was which.
Now, using electronic microscopes, Martin Smith at Cambridge University and his colleague Jean-Bernard Caron at the University of Toronto, have figured it out.
Their discovery was published in Nature.
Hallucigenia – a worm-like animal with legs and spikes along its back – lived 500 million years ago. It is the common ancestor of everything from tiny roundworms to lobsters.
The creature had a throat lined with needle-like teeth, a previously unidentified feature which could help connect the dots between it, modern velvet worms and arthropods.
“The early evolutionary history of this huge group is pretty much uncharted,” said Smith. “While we know that the animals in this group are united by the fact that they moult, we haven’t been able to find many physical characteristics that unite them.”
Hallucigenia was just one of the weird creatures that lived during the Cambrian Explosion, a period of rapid evolutionary development starting about half a billion years ago, when most major animal groups first emerge in the fossil record.
The video below shows how scientists believe Hallucigenia walked.