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Oldest known animal discovered from fossilized fat molecules

An international team of scientists led by The Australian National University (ANU) has identified the remains of the earliest known animal. The analysis of fat molecules in the fossilized remains revealed that the creature lived on the Earth approximately 558 million years ago.

The unusual animal, which is called Dickinsonia, grew up to 1.4 meters long and had an oval-shaped body covered in rib-like segments. Dickinsonia was part of the Ediacara Biota that lived on Earth 20 million years prior to the “Cambrian explosion,” which gave rise to more complex animals like the ones we have today.

A Dickinsonia fossil found by ANU PhD scholar Ilya Bobrovskiy near the White Sea in the northwest of Russia was so incredibly well-preserved that the tissue still contained molecules of cholesterol.

Senior researcher Jochen Brocks is an associate professor in the ANU Research School of Earth Sciences.

“The fossil fat molecules that we’ve found prove that animals were large and abundant 558 million years ago, millions of years earlier than previously thought,” said Professor Brocks.

“Scientists have been fighting for more than 75 years over what Dickinsonia and other bizarre fossils of the Ediacaran Biota were: giant single-celled amoeba, lichen, failed experiments of evolution or the earliest 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 palaeontology.”

Dickinsonia fossils contain invaluable knowledge about both the old world dominated by bacteria and the more modern world of large animals that emerged 540 million years ago during the Cambrian explosion. According to Bobrovskiy, the team developed a new approach to study these particular fossils.

“The problem that we had to overcome was finding Dickinsonia fossils that retained some organic matter,” said Bobrovskiy.

“Most rocks containing these fossils such as those from the Ediacara Hills in Australia have endured a lot of heat, a lot of pressure, and then they were weathered after that – these are the rocks that palaeontologists studied for many decades, which explained why they were stuck on the question of Dickinsonia’s true identity.”

Scientific analysis is typically focused on the structure of fossils, but the breakthrough in the current study came from extracting and analyzing molecules from inside of the Dickinsonia fossil.

“I took a helicopter to reach this very remote part of the world – home to bears and mosquitoes – where I could find Dickinsonia fossils with organic matter still intact,” said Bobrovskiy.

“These fossils were located in the middle of cliffs of the White Sea that are 60 to 100 meters high. I had to hang over the edge of a cliff on ropes and dig out huge blocks of sandstone, throw them down, wash the sandstone and repeat this process until I found the fossils I was after.”

ANU led the research in collaboration with scientists from the Russian Academy of Science, the Max Planck Institute for Biogeochemistry, and the University of Bremen in Germany.

The study is published in the journal Science.

By Chrissy Sexton, Staff Writer

Image Credit: The Australian National University (ANU)

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