Scientists have found the fossil footprints of a creature that walked the Earth 541 million years ago.
Dating back to the period just before the Cambrian explosion (when most complex animals first appeared), these ancient tracks represent the earliest known evidence of animal appendages.
The tracks were found in the Dengying Formation near the Yangtze Gorges in China.
"Animals use their appendages to move around, to build their homes, to fight, to feed, and sometimes to help mate," said geobiologist Professor Shuhai Xiao from Virginia Tech University.
"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."
The footprints are so small that they can only be seen by tilting the rock slabs at certain angles.
"The key challenge is to get the lighting right so that the fossils stand out against the background, because the fossils have very low relief," said Xiao.
