"We do not know exactly what animals made these footprints, other than that the animals must have been bilaterally symmetric because they had paired appendages", study co-author Shuhai Xiao, a geobiologist from Virginia Tech, told the Independent.
Scientists have found what they think is the oldest animal footprint in the fossil record, uncovering incredibly ancient track marks imprinted in the dirt as far back as 550 million years ago. In fact, the China discovery represents one of the earliest known records of animals evolving appendages.
An global team of scientists, including researchers from the Nanjing Institute of Geology and Palaeontology, and Virginia Tech in the United States, conducted the study.
Researchers on the study came from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences, and Virginia Tech in the United States. The new findings suggest animals evolved primitive "arms" and "legs" earlier than previously thought. That's hundreds of millions of years before dinosaurs started roaming Earth, about 245 million years ago. They are one of the most diverse animal groups in existence today.
Scientists have found fossilised footprints dating from 551 million years ago in China, left in mud by an unknown bug. "It is important to know when the first appendages appeared, and in what animals, because this can tell us when and how animals began to change to the Earth in a particular way".
"Animals use their appendages to move around, to build their homes, to fight, to feed, and sometimes to help mate", he said, adding that the movement of sediments by the first legged creatures could have had a major impact on the Earth's geochemical cycles and climate.
Unfortunately for scientists, the creature that made the footprints did not die nearby and leave an equally well preserved fossil to be studied. They hoped that the sunlight would reveal subtle marks left by ancient organisms on the Shibantan trackways.
Now, the discovery of the trackways and burrows shows that animals with appendages lived during the Ediacaran period, the researchers said.
This is a group of animals characterised by having paired appendages - in this case, perhaps, paired legs.
The animal appears to have paused from time to time, since the trackways appear to be connected to burrows that may have been dug into the sediment, "perhaps to mine oxygen and food", said the report.
The scientists are unsure whether the creature had many legs or just two, and whether it was a member of the arthropod group, which includes bumblebees and spiders, or annelids, which contains modern-day bristle worms.