540m-year-old bug tracks are oldest footprints ever discovered

The researchers speculate that the same creature left both the tracks and the burrows, suggesting an animal that scurried and tunneled its way across the ground.

While we don't know exactly when animals first left tracks on our planet, the oldest footprints ever found were left between 551 million and 541 million years ago during the Ediacaran period, a new study finds.

Prof Shuhai Xiao, a geobiologist at Virginia Tech University and senior author of the research, said the finding brings scientists closer to understanding what creatures were the first to evolve pairs of legs.

"The footprints are organised in two parallel rows, as expected if they were made by animals with paired appendages", Xiao told The Independent.

These trackways, preserved near burrows, were discovered in Dengying Formation - a rich fossil preserve in China's south - and constitute the first evidence confirming that an ancient group of animals called bilateria actually pre-dates the Cambrian explosion.

An global research team discovered the fossil tracks in China dating back to the Ediacaran Period, just before the Cambrian Explosion when life on Earth increased rapidly. The trackways are somewhat irregular, consisting of two rows of imprints that are arranged in series or repeated groups.

The remarkable discovery reveals how creatures with paired legs were scuttling around over 100million years earlier than previously thought.

The trackways' characteristics indicate that a bilaterian animal - that is, a creature with bilateral symmetry that has a head at one end, a back end at the other, and a symmetrical right and left side - made the tracks.

The presence of paired appendages (a primitive version of legs and arms) in the anatomy of this prehistoric creature is mirrored in the way the fossil footprints are laid out, Xiao explains.

The fossil tracks offer "some of the earliest known evidence for animal appendages and extend the earliest trace fossil record of animals with appendages from the early Cambrian (485 million to 541 million years ago) to the late Ediacaran period".

"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 the Earth in a particular way."

"At least three living groups of animals have paired appendages (represented by arthropods such as bumble bees, annelids such as bristle worms, and tetrapods such as humans)".

"Previously identified footprints are between 540 and 530 million years old". In fact, the China discovery represents one of the earliest known records of animals evolving appendages.

"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".