The bilaterian from 585 million years ago would have looked similar to this slug, but with no antennaes (Photo : Wikimedia Commons)
University of Alberta researchers have discovered trails left by a primitive slug-like creature that predates the previous earliest date for animals by 30 million years. This puts the new start date for the animal kingdom 585 million years ago.
The previous record holder was a find from Russia dating the earliest animal back to 555 million years ago.
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The tracks were made by a bilaterian, which is a small animal distinguished by its unique symmetry. The top side and the bottom side are virtually identical.
"The pattern of movement indicates an evolutionary adaptation to search for food, which would have been organic material in the sediment," says U of A paleontologist and co-author of the study Murray Gingras.
The tracks were made on silty sediment, came with no remains of the actual creature itself.
"Generally when we find tracks of a soft-bodied animal, it means there's no trace of the body because they fossilize under different conditions," said Gingras. "It's usually just the body or just the tracks, not both."
The age of the bilaterian was determined by running tiny granite particles in the sediment through mass spectrometry equipment, which determines how old something is by bombarding the material with lasers and analyzing the resulting atoms and molecules.
The findings will help scientists understand more about when and how animals came about, and what environmental stresses forced the behavior to seek out food.
"The challenge brought the sciences of geology, paleontology, geomicrobiology and geochronology together to nail down the age of the fossils," Kurt Konhauser, the team's microbiologist, said of the study.