‘Remarkable’ fossil discovery could be among the first animal trails ever

5 Sep 2019

The fossilised animal trail could be the among the first ever imprinted on the Earth. Image: Virginia Tech College of Science

Geoscientists have discovered what could be the first animal trails on the surface of the Earth, dating back half a billion years ago.

Researchers are hailing the discovery of a “remarkable” set of fossilised animal trail prints recently found in China. In a paper published to Nature by geologists and palaeontologists from Virginia Tech and the Chinese Academy of Sciences, it was revealed these prints are approximately 550m years old.

This means they could be among the first trails made by animals on the surface of the Earth. The discovery has been named Yilingia spiciformis – translating to ‘spiky Yiling bug’ – after the Chinese town near where the prints were found in multiple layers of rock.

The fossil trails are roughly the same age as bug-like footprints found by researchers during a series of digs between 2013 and 2018 in the Yangtze Gorges area of southern China, which date back to the Ediacaran period. This period of history predates the dinosaurs and even the formation of the ancient supercontinent Panagea.

“This discovery shows that segmented and mobile animals evolved by 550m years ago,” said Shuhai Xiao of Virginia Tech.

“Mobility made it possible for animals to make an unmistakable footprint on Earth, both literally and metaphorically. Those are the kind of features you find in a group of animals called bilaterans.

“This group includes us humans and most animals. Animals and particularly humans are movers and shakers on Earth. Their ability to shape the face of the planet is ultimately tied to the origin of animal motility.”

What it looked like

The spiky Yilang bug was a millipede-like creature, up to 2.5cm in width and up to 10cm in length. When it moved, it would drag its body across the muddy ocean floor while taking short rests, leaving trails as long as 60cm behind it. The creature had as many as 50 body segments including a left and right side, a back and belly, a head and a tail.

Bilaterans were a key moment in animal evolution, but until this discovery there was no convincing fossil evidence to tie them to the Ediacaran period.

This recent discovery may also be the first sign of decision-making by animals as the trails suggest an effort to move toward or away from something, perhaps under the direction of a sophisticated central nerve system.

Speaking of the discovery’s importance, Rachel Wood of the University of Edinburgh – a geologist not involved with the study – said it “is a remarkable finding of highly significant fossils”, adding that it “provides considerable insight into a major step in the evolution of animals”.

Colm Gorey was a senior journalist with Silicon Republic