Published: Fri, June 08, 2018
Sci-tech | By Patricia Wade

Earliest animal footprints found in China

Earliest animal footprints found in China

Researchers believe they may have been a type of arthropod - the family of animals with jointed limbs that includes insects and crustaceans, or something akin to a legged worm.

They are often assumed to have appeared and radiated suddenly during the "Cambrian Explosion" about 541-510 million years ago, although it has always been suspected that their evolutionary ancestry was rooted in the Ediacaran Period.

They are often assumed to have appeared and radiated suddenly during the so-called "Cambrian Explosion" about 541 to 510 million years ago, but scientists now tend to consider that their evolutionary ancestry was rooted in the Ediacaran Period.

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.

Researchers on the study came from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences, and Virginia Tech in the United States.

Animals left the first footprints on Earth up to 551 million years ago, according to ancient tracks found in China.

"If an animal makes footprints, the footprints are depressions on the sediment surface, and the depressions are filled with sediments from the overlying layer".

An global team of scientists, including researchers from the Nanjing Institute of Geology and Palaeontology, and Virginia Tech in the United States, conducted the study.

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Until now, there had been no evidence of limbed creatures prior to the Cambrian Explosion, say the researchers from Virginia Tech in the US. The latest prints date to the Ediacaran period, whose sparse fossil record is populated with soft-tissued creatures including worms and organisms that resembled tiny immobile bags.

This is a group of animals characterised by having paired appendages - in this case, perhaps, paired legs. Take that, rest of the pre-Cambrian life forms!

The trackways are the earliest discovered indication of when animals evolved appendages.

"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".

Still, due to the proximity of the track marks to fossilised burrows discovered nearby, the researchers hypothesise the creature may have exhibited "complex behaviour", such as periodically digging into sediments to mine oxygen and food among its riverbed habitat.

Bilaterian animals such as arthropods and annelids have paired appendages or "legs" and are among the most diverse animals today and in the geological past.

This is a sign of "complex behavior involving both walking and burrowing", the team argues in the paper.

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