When did animals leave their first footprint on Earth?

Pablo Tucker
June 9, 2018

The fossils date back to almost 3.5 billion years ago and are strong evidence of the earliest life that existed on Earth.

The fossilised footprints were discovered by a team of scientists studying trackways and burrows in China. This is considered the earliest animal fossil footprint record.

The tracks are from the Ediacaran Period, making them the first prints left by animals from that period.

Although it's not clear what animal left these ancient tracks behind - since only the trace fossils (evidence that an animal has been there) were discovered, and not the fossils themselves - the footprints date back 551 million to 541 million years ago, to the Ediacaran Period.

"They were probably made by millimeter-sized animals with bilateral appendages and can provide important insights into early bilaterian evolution and behaviors". At the moment, this is believed to be the first footprint ever left by an animal on Earth.

Still, this discovery means that paleontologists will have to revise their vision of how life developed in Earth's primordial oceans.

Researchers from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences in collaboration with the Virginia Polytechnic Institute and State University examined trackways and burrows in sediment dating back to the Ediacaran Period. In fact, the China discovery represents one of the earliest known records of animals evolving appendages. The scientists found the trackways in the Dengying Formation, a site in the Yangtze Gorges area of southern China.

Further, the footprints left behind by its multiple feet suggest that this sea-dwelling animal had paired appendages that raised its body above the ocean floor. They published their findings Wednesday in the journal Science Advances.

"The trackways are somewhat irregular, consisting of two rows of imprints that are arranged in series or repeated groups", explained notes from the Chinese Academy of Sciences. This new find is the first direct evidence of animals with appendages during the Late Ediacaran Period.

In a press release about the survey, Dr. Shuhai Xiao of Virginia Tech conveys, "If an animal makes footprints, the footprints are depressions on the sediment surface, and the depressions are filled with sediments from the overlying layer."This style of preservation is distinct from other types of trace fossils, for example, tunnels or burrows, or body fossils". It was after this point that arthropods (jointed limb insects like roaches and spiders) and annelids (ringed worms) completely took over the planet.

It's possible that the bodies were never actually preserved, so it may be that we'll never know what they actually looked like.

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