In a remarkable evolutionary discovery, a team of scientists co-led by a Virginia Tech geoscientist has discovered what could be among the first trails made by animals on the surface of the Earth, roughly a half-billion years ago.
Geosciences’ Shuhai Xiao called the unearthed fossils, including the bodies and trails left by an ancient animal species, the most convincing sign of ancient animal mobility, dating back about 550 million years. Named Yilingia spiciformis — that translates to spiky Yiling bug, Yiling being the Chinese city near the discovery site — the animal was found in multiple layers of rock by Xiao and Zhe Chen, Chuanming Zhou, and Xunlai Yuan from the Chinese Academy of Sciences’ Nanjing Institute of Geology and Paleontology.
The findings were published in August in Nature, and made headlines around the world, including CNN, BBC, The New York Times, and Smithsonian Magazine. The trials are from the same rock unit and are roughly the same age as bug-like footprints found by Xiao and his team in a series of digs from 2013 to 2018 in the Yangtze Gorges area of southern China. They date back to the Ediacaran Period, well before the age of dinosaurs or even the Pangea supercontinent. What sets this find apart: the preserved fossil of the animal that made the trail is a first step to understanding the mobility of early animals.
“This discovery shows that segmented and mobile animals evolved by 550 million years ago,” Xiao said. “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.”
The animal was a millipede-like creature a quarter-inch to an inch wide and up to 4 inches long that alternately dragged its body across the muddy ocean floor and rested along the way, leaving trails as long as 23 inches. The animal was an elongated narrow creature, with 50 or so body segments, a left and right side, a back and belly, and a head and a tail
The find also marks what may be the first sign of decision-making among animals — the trails suggest an effort to move toward or away from something, perhaps under the direction of a sophisticated central nervous system, Xiao said. The mobility of animals led to environmental and ecological impacts on the Earth surface system and ultimately led to the Cambrian substrate and agronomic revolutions, he said.
For further reading and a video on this historic discovery, visit Geosciences’ Shuhai Xiao finds fossils dating back 550 million years, among earliest known displays of animal mobility