In The Field

Burgess Shale Centenary: Decaying pizza

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. Some tell-tale hints in some pizza discs hint that maybe they are the slightly-decayed remnants of other, already-known species, he told the conference. Liu, who works in Martin Brasier’s group, has even rotted some modern jellyfish and seaweed bits in the lab and made modern fossils of them, to confirm that this does indeed create irregular, lumpy shapes (no huge surprise there). His conclusion – that blobby bits that don’t look like much might, in fact, be blobby bits that aren’t anything much special – is so intuitively obvious that I can’t help but think he’s right. Depending on who you talk to, though, downgrading the Pizza disc from a creature to a bit of garbage might be slightly controversial.

Posted on behalf of Nicola Jones


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