I love to go a wandering...
Fossils reveal earliest signs of mobility, researchers suggest.
Is this one of the first trails ever made by an animal on the surface of the Earth?
Quite possibly, says the team of palaeontologists that found unearthed fossils - including the bodies of ancient animal species and the trails they left - near the Chinese city of Yiling.
More to the point, their discovery shows that segmented and mobile animals had evolved by 550 million years ago, says Shuhai Xiao from Virginia Tech in the US.
"Mobility made it possible for animals to make an unmistakable footprint on Earth, both literally and metaphorically,” he says.
The fossils were found in multiple layers of rock by Xiao and Zhe Chen, Chuanming Zhou and Xunlai Yuan from the Chinese Academy of Sciences.
The animal now known as Yilingia spiciformis – which translates to spiky Yiling bug – was a millipede-like creature up to 10 centimetres long that dragged its body across the muddy ocean floor, resting along the way, leaving trails as long as 60 centimetres.
The fossils also reveal what may be the first sign of decision making among animals, Xiao says, as the trails suggest an effort to move toward or away from something, perhaps under the direction of a sophisticated central nerve system.
The findings are published in the journal Nature.