(Image: M.R. Smith/Smithsonian Institute)
In life this weird-looking fossil was a creature like a worm, although the spines, head and legs might suggest otherwise.
It belongs to a group of animals that roamed the ocean floor over 505 million years ago, during the Cambrian explosion of life. The palaeontologist Simon Conway Morris identified the genus among fossils found in the Burgess Shale in Canada’s Rocky Mountains, and thought it looked so strange that he named it Hallucigenia. That was in 1977, but until now no one has been sure just how to classify Hallucigenia in relation to modern animals.
So what did Hallucigenia look like when it was alive? Quite small – between 5 and 35 millimetres in length – but nevertheless it probably looked rather formidable, with ridged spines along its back and seven or eight pairs of clawed legs.
When the team looked closely at the claws, they realised that they were built like the jaws of velvet worms – which were already known to be modified legs.
“The peculiar claws of Hallucigenia are a smoking gun, and may even help to decipher other problematic Cambrian critters,” said Martin Smith, lead author of the research paper. “By deciphering ‘in-between’ fossils like Hallucigenia, we can determine how different animal groups built up their modern body plans.”
Journal reference: Nature, DOI: 10.1038/nature13576
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