At the moment, this is believed to be the first footprint ever left by an animal on Earth.
This means that the symmetrical creature appeared before the Cambrian Period, Chen noted.
These trace fossils represent some of the earliest known evidence for animal appendages and extend the earliest trace fossil record of animals with appendages from the early Cambrian to the late Ediacaran Period.
Bilaterians are one of the most common body types in the world, now and throughout history, but previous fossil evidence for them only goes back as far as the Cambrian.
The animal appears to have paused from time to time, since the trackways seem to be connected to burrows that may have been dug into the sediment, perhaps to obtain food.
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Scientists from the Chinese Academy of Sciences' Nanjing Institute of Geology and Paleontology and Virginia Tech have teamed together to find the prints and analyze them. The tracks seem to have been found in the mountainous Yangtze Gorges, in southern China.
"Animals use their appendages to move around, to build their homes, to fight, to feed, and sometimes to help mate", one of the researchers, geobiologist Shuhai Xiao from Virginia Tech University, told The Guardian. The rocks they come from are dated to between 551 million and 541 million years old.
Because the footprints are trace fossils, not fossils of the animal itself, it's going to be hard to credit a particular branch of the Tree of Life with the title of "First to Develop Limbs".
The researchers speculate that the same creature left both the tracks and the burrows, suggesting an animal that scurried and tunneled its way across the ground.
The members of the research team can't figure out whether the animal has two or more legs but they assume that the footprints may belong to a bilaterian- animals characterized by having paired legs.
"The footprints are organised in two parallel rows, as expected if they were made by animals with paired appendages".