500 million year old worm fossil discovered on ancient seabed

The worms were found hiding in ocean sediments. They even left their own footprints, with tiny “tunnels” as evidence.

Traces of these fossilized “tunnels” have been found in rocks collected decades ago from Canada’s Mackenzie Mountains in the Northwest Territories. But scientists only recently found the “mini-tunnels” after reanalyzing them.

Research by scientists has shed light on the region's ocean ecosystems during the Cambrian period (543 million to 490 million years ago), suggesting these environments may have contained more oxygen and more life.

The tunnels the worms leave in weathered rock are invisible to the naked eye and were discovered entirely by accident, said lead study author Brian Pratt, a professor of geosciences at the University of Saskatchewan in Canada.

Pratt and co-author Julien Kimmig, curator of the invertebrate paleontology collection at the Biodiversity Institute and Natural History Museum at the University of Kansas, found the tunnels while collaborating on another 2018 study.

Pratt and Kimmig were preparing samples for the 2018 study, sawing and grinding rocks, when they discovered something they had never seen before.

The preserved tunnel shapes are well-defined and have not collapsed, suggesting that the sediments around them were solid and "undisturbed," the study authors write.

The tunnels, which measured between 0.5 and 15 millimeters wide, were made by worms that ranged from about a millimeter to the size of a finger, according to the study. Most of the burrows were tiny, dug by worms that scoured ocean sediments in search of organic matter to eat.

In addition, the researchers found preserved worm bodies that were not burrowing worms, but contained pieces of body tissue that likely belonged to other worms.