Date of earliest animal life reset by 30 m years

30, June, cienceDaily

University of Alberta researchers have uncovered physical proof that animals existed 585 million years ago 30 million years earlier than previous records show.

The discovery was made by U of A geologists Ernesto Pecoits and Natalie Aubet in Uruguay. They found fossilized tracks a centimeter-long, slug-like animal left behind 585 million years ago in silty, shallow-water sediment.

A team of U of A researchers determined that the tracks were made by a primitive animal called a bilaterian, which is distinguished from other non-animal, simple life forms by its symmetry its top side is distinguishable from its bottom side and a unique set of "footprints.

"U of A paleontologist Murray Gingras says fossilized tracks indicate that the soft-bodied animal's musculature enabled it to move through the sediment on the shallow ocean floor.

"The pattern of movement indicates an evolutionary adaptation to search for food, which would have been organic material in the sediment," he said.

There were no fossilized remains of a bilaterian's body, just its tracks. "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."

It took more than two years for the U of A team members to satisfy themselves and a peer review panel of scientists that they had the right age for the bilaterian fossils.

U of A geochronologist Larry Heaman was among a group that returned to Uruguay to collect more fossil samples locked in a layer of sandstone.

Heaman says because the depositional age of the sandstone is difficult to determine, they focused their investigation on particles of granitic rock found invading the sandstone samples.

Heaman explains that the granitic rocks were put through the university's mass spectrometry equipment, a process in which samples are bombarded by laser beams and the resulting atom- to molecule-sized particles are analyzed and dated.

Over the course of his U of A career, Heaman has taken part in a number of breakthrough research projects involving fossils.

Last year he got the attention of the paleontology world when he confirmed the surprising date of a fossilized dinosaur bone found in New Mexico. Using U of A equipment, Heaman determined that the bone came from a sauropod, a plant-eating dinosaur that was alive some 700,000 years after the mass-extinction event that many believe wiped out all dinosaur life on Earth.