"Animals use their appendages to move around, to build their homes, to fight, to feed, and sometimes to help mate", he tells The Guardian, pointing out that the resulting movement of sediments may have had an effect on the planet's geochemical cycles and climate.
In a release put out by the Chinese Academy of Sciences- Nanjing Institute of Geology and Palaeontology, researchers noted that the fossils were from the Ediacaran Period- about 635-541 million years ago. "Unless the animal died and was preserved next to its footprints", said Xiao, "it is hard to say who made the footprints".
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.
On closer analysis, the team found the marks comprise two rows of imprints that they believe were left by a creature scurrying along a riverbed, at a time when life had not yet colonised dry land.
Still, this discovery means that paleontologists will have to revise their vision of how life developed in Earth's primordial oceans. The fossils date back to almost 3.5 billion years ago and are strong evidence of the earliest life that existed on Earth.
However, this creature - which provides the earliest evidence of an animal with legs - would have existed around 10 million years before then. This new find is the first direct evidence of animals with appendages during the Late Ediacaran Period.
An worldwide team of scientists, including researchers from the Nanjing Institute of Geology and Palaeontology, and Virginia Tech in the United States, conducted the study.
While the researchers are unable to identify the animal behind the footprints, there are three types of living animals with paired appendages: arthropods such as bumble bees, annelids such as bristle worms, and tetrapods which include humans.
"Arthropods and annelids, or their ancestors, are possibilities".
The trackways are the earliest discovered indication of when animals evolved appendages.
Also, the trackways appear to be connected to burrows, suggesting that the animals may have periodically dug into sediments and microbial mats, perhaps to mine oxygen and food.