‘Holy Grail of fossils’: mystery blobs revealed as earliest known animal

Christopher Davidson
September 21, 2018

The fat discovered in the new fossil has now settled that debate claiming Dickinsonia as the oldest known animal fossil. That conclusion comes thanks to fat, reports Phys.org. Now, an answer: Dickinsonia is an animal that dates back 558 million years, making it the earliest confirmed one in the geological record.

Scientists had been trying for years to find Dickinsonia fossils that retained some organic matter.

The study depends on the assumption that only animals can produce cholesterols, which some scientists suggest could be disproven as more research is conducted on the Earth's earliest inhabitants.

The fossils were discovered on two surfaces on a cliffside in the remote wilderness of north-west Russian Federation by PhD student Ilya Bobrovskiy, who is lead author on the paper, published in the journal Science..

Researchers found specimens of the creature, known as Dickinsonia, that was so well preserved they still contained molecules of cholesterol.

Now, an worldwide team of researchers has used modern chemistry to unearth striking evidence that Dickinsonia were indeed early animals. Most multicellular life leaves behind stable sterane hydrocarbons, which can be preserved in sediments for hundreds of millions of years.

"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", associate professor Jochen Brocks of the ANU Research School of Earth Sciences said in a statement. Unlike dinosaurs like the Tyrannosaurus rex or more recent extinct beasts like the wooly mammoth, fossils of Dickinsonia aren't particularly interesting to look at.

"However alien they looked, the presence of large dickinsoniid animals, reaching 1.4 m in size, reveals that the appearance of the Ediacara biota in the fossil record is not an independent experiment in large body size but indeed a prelude to the Cambrian explosion of animal life".

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The team from Australia, Russia and Germany retrieved Dickinsonia fossils in sandstone from Russia's White Sea region in what was a "totally serendipitous" discovery - Brocks compares it to finding a perfectly mummified T-rex in a swamp.

'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'.

An abundance of 27-carbon cholesteroids - mirroring the steroid composition of animal membranes - makes a convincing case that Ediacaran biota was at the forefront of the explosion of animal life during the Cambrian era roughly 514 million years ago.

"These fossils were located in the middle of cliffs of the White Sea that are 60 to 100 meters [197 to 328 feet] high", Bobrovskiy said.

Different teams of scientists have variously classified them as lichens, fungi, protozoans, evolutionary dead-ends and even as an intermediate stage between plants and animals. Finding the fat molecules helped settle the question of what exactly Dickinsonia was, and led to the monumental discovery.

There is evidence that hints at the existence of sponges 635 million years ago, though the oldest fossilized sponge is only 520 million years old.

Ultimately, Brocks said, understanding "what these strange-looking Ediacaran creatures really were.is essential if we want to understand the emergence and evolution of our own earliest ancestors".

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