Ancient mysterious creature that the classification challenged is an animal

An enigmatic creature who lived half a billion years ago is as "strange as life on another planet" and has been challenging the classification for nearly a century. But researchers can finally identify the mysterious organism as an animal – the oldest known animal on Earth – thanks to traces of old fats.

This precious organic evidence comes from exceptionally well-preserved fossils found in northwestern Russia, near the White Sea. The remains come from a strange organism called Dickinsonia. Dating from about 558 million years ago, Dickinsonia had an oval, segmented body, about 5 feet (1.4 meters) long, and lacking physical features generally associated with animals, such as discernible limbs, orifices or organs, or a discernible head.

For decades, the strange bodies of Dickinsonia and other peculiar creatures of that era – the Ediacarans, about 635 million to 541 million years ago – made it difficult to place these creatures on the tree of life with certainty. But the recent discovery of news Dickinsonia The fossils revealed something that had never been seen in this type of fossil before: organic tissues preserved in the fossilized impression left by the body of the creature. From this print, or from the biofilm, researchers were able to identify cholesterol molecules, a fat recognized as a "feature" of animals, scientists reported in a new study. [Images: Bizarre, Primordial Sea Creatures Dominated the Ediacaran Era]

"Scientists have been fighting for over 75 years on what Dickinsonia Jochen Brocks, associate professor at the School of Earth Sciences Research of the Australian, and co-author of the study, Jochen Brocks, associate professor at the School of Research in Earth sciences of the Australian, and other strange fossils of Ediacaran biota, lichens, failed experiments in evolution or the first animals on Earth. National University (ANU), said in a statement.

"Fossil fat now confirms Dickinsonia as the oldest known animal fossil, solving a decades-old mystery that has been the holy grail of paleontology, "said Brocks.

Who is the oldest?

The first forms of life on Earth were microbes; the earliest known examples have been traced to rocks dating back 3.95 billion years. Animal life did not emerge until billions of years later, with many complex animal forms appearing during a dramatic explosion of evolution during the Cambrian explosion, which followed the ediacarian era and lasted up to 490 million years.

But what were the first animals? It's hard to pin down because fossil evidence of soft-bodied creatures is rare. Sponges have long been considered the most primitive animals, because of the simplicity of their body plan. But although there is evidence of their presence 635 million years ago, the oldest fossilized sponge remains have only 520 million years.

According to a study published in 2017, jellyfish could be even older than sponges. However, this conclusion was drawn from genetic analysis and not from fossil evidence.

A fossil coat rack

Most known Dickinsonia Ilya Bobrovskiy, PhD student at ANU, co-author of the study, said in a statement that the fossils come from places where the rocks have been subjected to intense weather due to heat and heat. pressure, destroying any trace of organic matter. On the other hand, the remote Russian site offered the possibility of finding fossils in better condition – but their arrival has proved to be a real obstacle, Bobrovskiy discovered.

"These fossils were located in the middle of the cliffs of the White Sea, between 60 and 100 meters [197 to 328 feet] high, "said Bobrovskiy. I had to hang the edge of a cliff on ropes and dig huge blocks of sandstone, throw them, wash the sandstone and repeat this process until I found the fossils I was looking for. "

Although many members of the paleontology community have long suspected Dickinsonia was a real animal, the new study "puts the nail in the coffin" of all the other assumptions about this unusual creature, Roger Summons, professor of geobiology at the Department of Earth Sciences, Atmosphere and Planets of the Massachusetts Institute of Technology Science live.

According to Summons, who did not participate in the study, now that scientists have demonstrated that this particular site and this collection of fossils is fertile ground for molecular analysis, much more work will follow to unravel the mysteries of animals old as Dickinsonia.

"You can go so far in looking at form and shape – morphology, size, that sort of thing – but nothing better than the molecular record to tell you more precisely where these organisms fit into the big picture. set of things "I said.

The results were published online today (Sept. 20) in the journal Science.

Original article on Live Science.