About 550 million years ago, creatures walked across a sea bed and left their imprints.
These footprints, discovered at a fossil bed in South China known as the Shibantan Member of the Dengying Formation, and revealed in the journal Science, constitute the earliest known trackways ever found.
The footprints are “arranged in a poorly organised series or groups” write a team of palaeontologists led by Zhe Chen from the Chinese Academy of Sciences in Nanjing.
The markings suggest that the responsible organism – the identity of which is likely to remain forever unknown – moved with the aid of bilateral appendages that lifted it above the sediment.
The find is significant, because creatures with such appendages appear suddenly – and in great variety – during the so-called Cambrian explosion, which began about 540 million years ago. The mysterious animal that left its mark some 10 million years earlier shows that bilateral locomotion was present during the preceding Ediacaran period.