Ancient trace fossils could shed light on evolution of complex animals

Newly discovered trace fossils left by some of the first organisms capable of active movement could change the way scientists view the evolutionary timeline, a new study published in Nature Ecology & Evolution reports.
By Billy Kirk | Sep 13, 2017
Newly discovered trace fossils left by some of the first organisms capable of active movement could change the way scientists view the evolutionary timeline, a new study published in Nature Ecology & Evolution reports.

The remains -- which were first found by a team of international researchers -- are not physical fossils like bones. Rather, they are tracks and burrows left behind by some of the oldest complex organisms on Earth.

Scientists first uncovered the ancient burrows in the Corumb region of western Brazil. They then used a process known as X-ray microtomography to visualize the tiny remains. This process allowed them to create a virtual, 3D model of the tunnels without the risk of harming them.

Though they are not sure, the team believes the marks were left behind by "nematoid-like organisms" that were similar to modern-day roundworms. In addition, as the burrows measure between 50 to 600 micrometers -- one thousandth of a millimeter -- in diameter, the creatures would have measured no bigger than a human hair.

The fossils date back to a geological and evolutionary period known as the Ediacaran-Cambrian transition. They are important because, while current dating techniques suggest that the first animals appeared before the recently discovered burrows, the new research shows the fossils pre-date animals.

"This is an especially exciting find due to the age of the rocks - these fossils are found in rock layers which actually pre-date the oldest fossils of complex animals - at least that is what all the current fossil records would suggest," said study co-author Russell Garwood, a researcher from The University of Manchester's School of Earth and Environmental Sciences, according to Daily Mail UK.

The burrows also reveal that complex animals with muscle control existed around 550 million years ago. Not only does that suggest findings such as this one may have been overlooked in the past, but it also means bilaterians -- a term that refers to complex animals with bilateral symmetry -- are younger than previously believed.

If the new dates are correct, the remains could give scientists a new glimpse into the Ediacaran-Cambrian transition, which is one of the most important evolutionary points in history. Many animal groups that are alive today appeared during that time, and study of the age could help build a better evolutionary tree.

The team believes the fossils give an "unexplored window for tracking animal evolution in deep time,"International Business Timesreports.

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