Previously, it was thought that bilaterian animals first appeared between 541 and 510 million years ago during the Cambrian Explosion, a period where primitive life on Earth suddenly started evolving into new and diverse forms, but these little footprints are estimated to be between 551 and 541 million years old, placing them in the Ediacaran period.
They are often assumed to have appeared and radiated suddenly during the Cambrian Explosion about 541 to 510 million years ago, although it has always been suspected that their evolutionary ancestry was rooted in the Ediacaran Period. They have published their findings in the journal Science Advances on June 6.
Pretty old, right? Well, no, not compared to the footprints just discovered in the Dengying Formation in southern China-these marks are the first known evidence of feet.
"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", Xiao explains. However, Xiao said they are uncertain if the creature belonged to the arthropod family or whether it has many or two legs.
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.
"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.
Prior to this, animal life on Earth consisted of simpler, single-celled or multicellular organisms, but the Cambrian Period gave rise to more complex creatures of a kind we recognise today, including bilaterian animals, who exhibited the first bilateral symmetry.
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.
Researchers do not know what animals made the footprints but have interpreted the two parallel rows of dots as rows of tracks.
"Although the exact identity of the trace maker of the Shibantan trackways is hard to determine in the absence of body remains at the end of the trackways, we suggest that the trace maker was probably a bilaterian animal with paired appendages", the authors reported.
It's possible that the bodies were never actually preserved.