A Dickinson jellyfish that looks like a pancake set a new record for the oldest animals

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About 558 million years ago, something strange-looking died on the bottom of the ancient ocean. This east-west body is about 5 centimeters long and oval-shaped, with a line in its middle, and symmetrical "ribs" on the left and right that connect this line. After death, the thing was quickly buried by sediment and gradually turned into fossils.

The world around it changed, and this thing has remained so until it is fossilized to this day. Before the division moved, the landblock on Earth was a merging supercontinent. In the ocean, life explodes. For the first time on Earth, some creatures with eyes, mouths and hard shells appeared. Some of the earliest life began to travel to land, first in mossy lichens and then active in huge forests. Insects first crawl on the ground, then grow wings and appear in the sky. The Dinosaur Empire experienced rise and fall. Mammals eventually took over the planet, and humans among mammals were particularly powerful. Among them, a man named Ilya Bobrovskiy excavated the rib-shaped oval fossil mentioned above in his resting place.

All the researchers said that 558 million years is a very long time.

Despite the very long course of time, scientists have found that there are still many simple molecules in the cells of this oval creature! Geochemist Bobrowski of the Australian National University separates, measures and identifies these molecules. The scientists eventually provided conclusive evidence that the creature was an animal, despite its peculiar appearance. More specifically, it's the oldest animal ever discovered, and the animal's name is Dickinsonia.

First discovered in the 1940s, the Dickinson jellyfish is the most representative member of the Ediacaran biota, a group of mysterious mollusks that existed between 541 million and 570 million years ago. In a world controlled by microbes, these soft organisms are the first known large, complex organisms on Earth. These creatures can be seen with the naked eye, and these creatures even have eyes.

But what exactly are these creatures? Some look like big leaves. There are other organisms that we already know today, which one scientist described as "strangely alien-like, but relatively easier to study." "Some paleontologists, including the original discoverer of Dickinson jellyfish, classify these creatures as animals, viewing them as precursors to the more common life forms that emerged during the Cambrian explosion of life. Others see it as a giant version of a single-celled amoeba-like protists, lichens, colonies, and even as a completely extinct life, the realm of which is a technical term in biological classification.

Bobrovsky recently proposed a new way to resolve these controversies. While observing Ediacaran biological fossils under a microscope, Bobrovsky discovered distinguished dark compositions. This is clearly a feature left by organic compounds after decay in the body of their "owner". After the organism dies, large and complex molecules like DNA and proteins don't survive for long, but smaller, more stable molecules can survive for a long time. If Bobrovsky could recover these small molecules, he could find unique chemical signatures that distinguish animals from other bacteria and the biological world. "My thesis advisor, Jochen Brocks, said we could give it a try, but he was always convinced it was a stupid idea," Mr. Bobrovsky said. "Even I thought I would fail, but in the end I didn't fail."

Bobrovsky dug up 8 new Dickinson fossils from a place called Lyamtsa on the edge of Russia's White Sea. Bobrovsky used solvents to extract some organic molecules from these specimens and then identified all the chemical components in the extract. Bobrovsky was looking for traces of a specific group of steroids.

When people think of steroids, they often think of illegal drugs that help improve competition performance, or supplements that increase muscle, but steroids have a broader meaning. Steroids here refer to chemicals found in the cells of all complex organisms, including animals, protists, and fungi. There are different types of steroids, and different steroids are different indicators of different biota.

For example, Bobrowski found that the clay and sandstone sediments around Dickinson's fossils had steroid-rich characteristics, specifically suggesting green algae. In contrast, the steroids in Dickinson's fossils are almost entirely cholesterol deposits. This precludes the possibility that Dickinson was a lichen or protégé, as Dickinson contained very different steroid mixtures. This also excludes the possibility of being colonies, as they simply do not produce steroids. In fact, only one group of organisms produces cholesterol, and that is animals. So Dickinson and we are in the same category.

"I also wish Dickinson were something else strange and strange, but the only possible explanation for now is animals," Pobrowski said.

"Is the Ediacaran biota a prelude to a complex animal-dominated ecosystem, or a failed evolutionary attempt?" To understand this problem, it is necessary to understand the emergence of biological complexity on Earth," said Lidya Tarhan of Yale University. Bobrovsky's study does not completely solve this problem, because it does not say that Dickinson was the precursor of any identifiable animal, nor does it mean that he was part of an extinct group. But the study does show that the roots of the animal kingdom are deeper than many scientists know.

"It's a good study," said Jennifer Hoyal Cuthill, who studies the Ediacaran biota at the University of Cambridge in the United Kingdom. "It's fantastic that the biomolecules of these animals have survived for more than 500 million years and have their secrets revealed by scientists."

Alexander Liu, who also works at cambridge, added that extracting such molecules was "unimaginable a few years ago". These molecules can provide evidence to support other studies investigating how organisms grow and develop. "Now, I think there's very strong evidence that Dickinson was an animal," Alexander said.

"Can this method be applied to members of the Ediacaran biota who are equally to be identified as Dickinson before them?" This idea is exciting and exciting. If we could, we could start reconstructing the Ediacaran biota," Talhan added. Not every member of a biota will be an animal. For example, before Bobrowski studied Dickinson, he tested his technique on another fossil called Beltanelliformis that was different from Dickinson's, and the results showed that this round, 1.27 cm diameter thing was a colony.

"What are the other components in the Ediacaran biota? It's a very open question," Pobrowski said. "They could still be anything else." But the key is whether the researchers can determine exactly what these things are. The mysteries of the Ediacaran biota have remained so long that it now seems that it may not take us long to unravel these secrets. It's a puzzle, it's a puzzle with an answer, it's a puzzle where you can find the answer.

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