Some of the weirder Ediacaran species might not be species after all, Alexander Liu of Oxford University has told the conference. There’s a brand of squidgy Ediacaran fossils known collectively as ‘pizza discs’. They are all round, and have bumpy bits – of up to 1-cm height in the fossil record – randomly scattered in the middle. These bumps are not consistent from one pizza disc to the next – each disc is individual. This makes it hard to identify the characteristics that define the creature that left the fossil print. So hard, in fact, that Liu wonders if it’s not a specific creature after all.