550 million years ago, in present-day China, a worm-like animal crawled across the muddy seabed, took a short break, leaving a clear imprint of its belly, crawling a little further and dying. His traces were preserved over the millions of years – a stroke of luck for researchers. The fossils are one of the oldest evidence of mobility.
The ability to move was a breakthrough in evolution. While the world’s first living beings passively roamed the water, mobility brought independence and the chance to conquer new habitats. When the world learned to run, however, is not definitively clarified. The proof is difficult. Although researchers keep finding suspicious imprints in sediments, it has been difficult to determine – until now – whether they actually came from a crawling animal.
The special thing about the current fossil find is that it not only provides 550 million-year-old creep traces, but also the animals that left them behind. The creatures, which are up to 27 centimeters long, are reminiscent of centipedes or worms in the form of a wheat nut with their elongated shape.
Twice the age of the oldest dinosaurs
The animal, named Yilingia spiciform, lived in the Ediacarium – the time before the Great Species Explosion of the Cambrian around 540 million years ago, when many of today’s animal tribes emerged. By comparison, the first dinosaurs lived about 235 million years ago and died out 66 million years ago.
Until now, hardly any animals were known from the Ediacarium, the researchers led by Shuhai Xiao of the Chinese Academy of Sciences in Nanjing report in the journal “Nature”. The fossil that has now been discovered shows that the first mobile animals must have been created at that time.
The name Yilingia comes from the district of Yiling, where the fossils were discovered. The fact that the animal was already moving in a targeted manner at that time could indicate an already developed central nervous system.
So far, the researchers do not know where to place the unusual worm in the family tree of life. For example, the annelids – i.e. ringworms – or the arthropods – i.e. arthropods, which include insects, centipedes, and spider animals, would be possible.