The oldest animal.

The Guardian pulls back the veil – using fossilized cholesterol, of all things – on what could be the world’s oldest animal – an oval-shaped creature that lived on the ocean floor 558 million years ago in what’s now far northwest Russia:

The new fossils, of the genus Dickinsonia, are the remains of an oval-shaped lifeform and part of an ancient and enigmatic group of organisms called Ediacarans. These creatures are some of the earliest complex organisms on Earth, but their place within the evolutionary tree has long puzzled scientists. Suggestions as to what they were have ranged from lichens to failed evolutionary experiments to bacterial colonies.

Now, by identifying the remains of organic matter on newly discovered Ediacaran fossils as ancient cholesterol, the scientists have been able to confirm Dickinsonia was an animal, which makes it the oldest known animal.

“It is the exact type and composition of that fat that was the giveaway that Dickinsonia was in fact an animal,” said Jochen Brocks of the Australian National University, one of the authors on the study. He added that the study solves “a decades-old mystery that has been the holy grail of palaeontology”.

“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,” [PhD student Ilya] Bobrovskiy said.

“These fossils were located in the middle of cliffs of the White Sea that are 60-100m 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.”

Charlotte Kenchington, a palaeobiologist based at the University of Cambridge, said: “It’s really, really unusual to have preservation of organic matter in the Ediacaran. The really neat thing about this study is that they’ve analysed both the sediment around the fossil and the fossil itself.

“The biomarker signal of the sediment is very different to the biomarker signal of the organic matter associated with the fossil. This gives you a huge deal of confidence in the results.”