Burrowing tracks made by a centimetre-long prehistoric slug have pushed the earliest traces of animal life back 30 million years.
The soft-bodied creature left its marks in a region of silty sediment in central Uruguay called the Tacuari Formation.
Rock dating has determined that the tracks are 585 million years old, 30 million years older than any previously known animal traces.
Unlike simpler life forms, true animals such as the slug are “bilaterian” and have a front and back as well as an upper and lower side.
The findings suggest bilaterian animals appeared during the early Ediacaran period, which pre-dates the “Cambrian explosion” when life diversified into myriad forms.
The findings, by a team from the University of Alberta in Canada, are reported in the journal Science