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WASHINGTON – A strange fossil that looks a bit like a giant leaf, or a footprint the size of a coffee table, has intrigued scientists for decades.
Was it a mossy plant? A giant unicellular amoeba? A failed experiment in evolution? Or the first animal on Earth?
After digging one of these fossils on a cliff in Russia and analyzing its contents, researchers discovered molecules of cholesterol, a type of fat.
And they found their answer. The creature, known as Dickinsonia, is the first known animal on Earth. "Scientists have been fighting for more than 75 years" about the nature of these "weird fossils," said Associate Professor Jochen Brocks from the School of Earth Sciences Research at Australian National University. "The fossil fat now confirms Dickinsonia as the oldest known animal fossil, solving a decades-old mystery that has been the holy grail of paleontology."
The results are published Thursday in the American journal Science.
Dickinsonia contained vein-like segments along the entire length of his oval shaped body, up to 4.4 feet (1.4 meters).
The analysis showed that animals were plentiful 558 million years ago, millions of years earlier than expected, according to Brocks.
The creature was part of the Ediacara biota that lived on Earth at a time when bacteria reigned, 20 million years before the emergence of modern animal life – a period known as the Cambrian explosion. .
Scientists have struggled to find Dickinsonia fossils that still contain organic matter.
Many known fossils were found in Australia and had been exposed to too many elements over millions of years.
The fossil of the current study comes from cliffs located near the White Sea in northwest Russia.
"I took a helicopter to reach this very remote area of the world – where bears and mosquitoes live – where I could find Dickinsonia fossils whose organic matter was still intact," said researcher Ilya Bobrovskiy. l & # 39; ANU.
"These fossils were located in the middle of the cliffs of the White Sea, which are between 60 and 100 meters high. I had to hang the edge of a cliff on ropes and dig huge blocks of sandstone, throw them to the ground, wash the sandstone and repeat this process until I found the fossils I was looking for.
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