Ancient worm fossil rolls back origins of animal life

More than half a billion years ago, a strange, worm-like creature died as it crawled across the muddy sea floor. Both the organism and the trail it left lay undisturbed for so long that they fossilised. Now, they are helping to revise our understanding of when and how animals evolved.

The fossil, which formed some time between 551 million and 539 million years ago, in the Ediacaran period, joins a growing body of evidence that challenges the idea that animal life on Earth burst onto the scene in an event known as the Cambrian explosion, which began about 539 million years ago.