Fossilized trails left in 560-million-year-old Canadian rocks may be some of the earliest evidence of squirming animals. Latha Menon at the University of Oxford, UK, and her team studied the disk-shaped impressions left by an organism called Aspidella in what was once shallow water in Newfoundland. The authors identified previously overlooked horizontal and vertical rock trails that seemed to be linked with Aspidella. They suggest that the marks were made as the animals wormed their way out of sediment, rather than as they passively slid. Aspidella, and perhaps other Ediacarans, were probably early animals living underwater, the authors say.

Geology http://dx.doi.org/10.1130/G34424.1 (2013)