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September 24, 2018 – Scientists from the Australian National University (ANU) and overseas discovered fat molecules in an ancient fossil to reveal the oldest confirmed animal in the geological record that lived on Earth there 558 million years ago.
The strange creature named Dickinsonia, which reached 1.4 meters long and was oval-shaped with segments resembling veins along its body, was part of the Ediacaran biota that lived on Earth 20 million years ago. years before the modern Cambrian explosion. animal life.
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Ilya Bobrovskiy, a doctoral researcher at ANU, discovered a well-preserved Dickinsonia fossil in a remote area near the White Sea in northwestern Russia, that the tissues still contained cholesterol molecules, a type of fat characteristic of animal life.
Jochen Brocks, Senior Research Associate, said the Cambrian explosion was the fact that complex animals and other macroscopic organisms – such as molluscs, worms, arthropods and sponges – were beginning to dominate the fossil record.
"The fossil fat molecules we found prove that animals were large and abundant 558 million years ago, millions of years earlier than expected," said ANU Associate Professor Jochen Brocks.
"Scientists have been fighting for over 75 years on what Dickinsonia and other strange Edicaran biota fossils were: unicellular giant amoebae, lichens, failed experiments in evolution or the first animals on Earth . 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.
Mr. Bobrovskiy said the team had developed a new approach to study Dickinsonia fossils, which hold the key between the old world dominated by bacteria and the world of large animals appeared 540 million years ago when the Cambrian explosion.
"The problem we had to overcome was to find Dickinsonia fossils that held organic matter," said Dr. Bobrovskiy of the ANU School of Earth Sciences Research.
"Most of the rocks containing these fossils, like those in the Ediacara Hills in Australia, have been subjected to a lot of heat, a lot of pressure, and they have been altered – the rocks that paleontologists have studied for decades. explains their were stuck on the issue of Dickinsonia's true identity. "
Palaeontologists normally study the structure of fossils, but Mr Bobrovskiy extracted and analyzed molecules from inside the Dickinsonia fossil found in ancient rocks in Russia to make a decisive discovery.
"I took a helicopter to reach this very remote region of the world – where bears and mosquitoes live – where I could find Dickinsonia's fossils with still intact organics," said Mr. Bobrovskiy.
"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.
Associate Professor Brocks said that studying molecules from these ancient organisms was a game of chance.
"When Ilya showed me the results, I could not believe it," he said.
"But I also immediately saw the meaning."
The ANU led the research in collaboration with scientists from the Russian Academy of Sciences and the Max Planck Institute of Biogeochemistry and the University of Bremen in Germany.
The research is published in Science.
Link to the summary of this article on sciencemag.org: http://science.sciencemag.org/cgi/doi/10.1126/science.aat7228
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