The "Dickinson Jellyfish" is one of the oldest animals on Earth

Are the creatures that left this mark animals, protists, or fungi? Chemistry offers new clues. PHOTOGRAPHY BY O. LOUIS MAZZATENTA

According to National Geographic (written by Maya Wei-Haas, compiled by Huiyuan Zhong): This mysterious thing is one of the oldest animals on Earth.uux.cn This strange creature has long plagued scientists. So a team of researchers used modern analytical techniques to re-examine this ancient monument.

Edicaran biotas are a quirky bunch—including coiled discs with rings, striated clumps, uneven cords, and wavy leaf-shaped objects. These soft, unscathed creatures occupied warm shallow seas 570 million years ago and were the first complex creatures to appear on Earth.

Dickinsonia, commonly translated as "Dickinson jellyfish", is a well-known species in this group of creatures. This flat, ribbed, oval creature can grow to more than 120 centimeters in diameter with a pronounced ridge in the center. What exactly Dickinsonia is, however, has puzzled scientists for a long time. This strange creature has been classified several times in history by scientists into different realms, and almost every realm has been spent. The controversy in recent decades has revolved around three taxa: some say it's fungi, some say protists, and some say it's animals.

A new study published this week in the journal Science is one in which researchers use modern technology to revisit this ancient creature. Their findings, along with additional evidence, suggest that Dickinsonia may be one of the earliest animals ever discovered, earlier than the Cambrian explosion, 541 million years ago and the origin of most of the major animal taxa in existence.

"We're already part of the study," said the study's author, Jossen José, a paleontological geochemist at the Australian National University. Jochen Brocks said. "It's an animal." Although Dickinsonia eventually went extinct, the animal was one of many species that led to early experiments on multicellular biology that eventually led to our modern animal garden.

"I think that's somehow a solution to our confusion about Dickinsonia." Paleontologist Mary of the University of California, Riverside. Mary Droser said she was not involved in the study.

Over the past few years, she explained, paleontologists have reached a broad consensus based on studies of Dickinsonia's imprints that Dickinsonia is an animal. The new study builds on this evidence and continues to delve deeper, using chemistry to support this animal hypothesis. "It's really helpful for putting Dickinsonia into the animal evolutionary veins of Earth." Droser said.

What is Ediacaran Biology?

First discovered in 1946 in the Ediacara Hills of the Flinders Ranges in southern Australia, this group of evolutionary geeks is very different from living creatures. Edicaran creatures are "weird like creatures from another planet, but relatively easy to reach," paleontologist Adolf Hitler said. Adolf Seilacher described this in a 2007 paper published in the Geological Society of London, Special Publications.

Their appearance indicates that evolution is testing the body shape of organisms as they transition from small to large. There are more than 50 known species of Ediacaran organisms, and they have been found on every continent except Antarctica.

By studying when large organisms suddenly appear on Earth, scientists can gain a deeper understanding of the formation of complex organisms. The study could also shed some clues about how creatures appeared in that distant world. Compared to the scare studies on other planets, "it's really cheaper to go back in time and see how life unfolded on Earth." Droser said.

How to study something that doesn't exist

One of the challenges of studying Ediacaran biology is the problem of preservation. Their soft bodies have long since rotted away, and they have no bones or shells to remain in the fossil record. This means that we can mostly see the appearance of these ancient inhabitants by the imprints or traces left by them—there are many detailed features that cannot be seen at all from the rough marks. These creatures were also fairly early members of the evolutionary tree, very different from today's organisms, so it is difficult to classify them. In the 1980s, some scholars even proposed that Edicaran organisms should be extinct in their own right.

Past research has focused on the physical analysis of Dickinsonia's legacy—growth and development, evidence of movement, body size, and complexity. In this latest study, scientists turned to molecular biomarkers called sterols in search of new clues. Many animals make sterols, but each taxon is slightly different.

Animals make sterols called cholesterols, "like we found in mcGonagall." Bullocks joked. But Ediacara bio doesn't eat fried food. These compounds play a very important role in the cell membranes of almost all animals, helping to control the entry and exit of substances.

Scientists have long begun to use biomarker analysis methods to look for algae in large amounts of sediment. "In this example, you get the average composition of the local ecosystem," Ilya said. Ilya Bobrovskiy said he was the lead author of the new study and a PhD student at the Australian National University.

Because most of the creatures of Ediacara leave behind their appearance marks, no one has ever tried to test the biomarks of these ancient geeks. However, the fossil imprints of some Ediacaran organisms still retain a thin layer of organic matter. And Pabrowski believes that the carbonaceous bonds on these organic films may hide the secret of the true identity of these strange creatures.

Bhabroski's supervising professor, Bullocks, was originally skeptical. "At first I thought it was a crazy idea." He said. But in order not to hit the ambitious student, he let him do it anyway.

What is the significance of the later analysis results?

Pabrowski developed a method to test the sterols left on fossils by the Edicaran organism and compare them with biomarker results extracted from surrounding rocks.

To test this approach, Pabrowski first studied the Beltanelliformis fossil in the Ediacaran biota. The creature used to be thought to be associated with algae, fungi, and even jellyfish. As a result, its biomarker indicates that it is a globular community of blue-green algae. Earlier this year, they published the analysis in the journal Nature Ecology and Evolution.

The team then turned to Dickinsonia and took samples from the White Sea region in northwestern Russia.

"The molecular composition of these fossils and the molecular composition of the seabed around the fossils are really black and white." Brox said. Fossil traces contain large amounts of ancient cholesterol — as high as 93 percent — suggesting that it was an animal. The surrounding seabed is found in very few amounts, with ergosteroids instead, showing the presence of green algae.

The simplicity of the analysis is part of what makes the new study so remarkable. "It's a very creative way to solve this problem," said Paula Thompson, a microbiologist at Stanford University who was not involved in the study. Paula Welander said, "This is the kind of 'how no one thought about it before?'" thing."

This method should be of great help in understanding other mysterious Edicaran creatures, such as Oxford Paleontologist and mathematician Renee, who was also not involved in the study. Renee Hoekzema said in an email. She was most interested in the chemical analysis of feathery leaf-like morphological life (rangeomorphs), which may be related to Dickinsonia and one of the next targets for Bullocks and the research team.

"These are exciting times." Hosama said. "After 70 years of debate, we finally began to understand the mysterious nature of Ediacaran creatures."

How long can biomarkers last?

Over time, all organic matter breaks down, and cholesterol is no exception. Brox noted. But the products produced when cholesterol decayed were very special, he explained, and the "original skeleton of cholesterol" remained in these molecular fossils.

Wielander, who studied the production and function of modern sterols in order to go deeper into ancient traces, praised the cruelty of the work, noting that the team "really took care of every detail very carefully." 」

Of course, in the world of science, nothing is absolutely certain. The study is based on the hypothesis that only animals produce cholesterol, and Wieland points out that this is okay with current data, but that could change as we learn more about the many life forms on Earth.

"There are so many uncertain places." It is Pabrowski's description of the work of such ancient creatures. "But applying biomarkers can solve a large part of the uncertainty."

Droser added: "With all the other information, it's really hard to argue that this isn't an animal."

So, was Dickinsonia the first animal?

While scientists can't yet pinpoint exactly when the first animals appeared, ancient traces suggest that it must have been more than 600 million years ago. However, Dickinsonia's taxonomic hierarchy has only recently been confirmed, and it is located among the oldest fauna ever discovered. Kimberella is an early mollusk-like animal, comparable to dickinsonia's time. There is also a creature of the form of a worm that may have left a fossilized sinuous footprint called Helminthoidichnites.

About 541 million years ago, the wet, soft Ediacaran creatures gave the world to the strange animals covered with spines and armor during the Cambrian explosion.

Together, these two diverse classes of early creatures can help us gain a deeper understanding of all the creatures that swim, jump, fly, run, and wobble around the world today. "We're amazed at the diversity of life and how living things adapt to the different environments on this planet," Droser said. "But these are the result of the evolution and extinction of the last 1 billion years on Earth... The Ediacaran biota is where it all started."

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