Traces of an ancient arthropod found in Nevada (USA) indicate that living creatures used limbs for movement at least 30 million years earlier than previously thought
A report on the Nevada find by Ohio University Professor Loren Babcock and his colleagues was presented in Houston at a meeting of the Geological Society of America.
The tracks - two parallel rows of small dots, each about 2 millimeters in diameter - date from about 570 million years ago, the Vendian (Edicarian) period, which predated the Cambrian, when most groups of today's animals appeared.
Previously, scientists believed that only microorganisms and simple multicellular animals existed on Earth in the Precambrian era, but this idea has changed, Babcock explains.
“We talked about the possibility of more complex creatures in the Edicarian period - corals, some arthropods and flatworms, but the evidence was not entirely convincing. But if you find, as we do, evidence of animals with legs, it makes that possibility more likely,”says the scientist, quoted in a report from Ohio University.
Babcock found footprints near Goldfield, Nevada. According to him, the creature, which was most likely an arthropod resembling modern centipedes, had to tread on soft marine sediments, since its legs only left small indentations.
Scientists could not determine the body length of this creature or the number of limbs, but, judging by the tracks, it was an animal about a centimeter wide, with many thin legs.
In 2002, it was reported that similar footprints were found, which were dated to the mid-Cambrian period - about 520 million years ago. Similar footprints have also been found in southern China and date back to 540 million years ago.
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The find, made by Babcock and his colleagues, is not only the oldest known evidence of limb-propelled animals, it also shows that complex organisms lived on Earth before the Cambrian period.