The Ediacaran critters were an odd bunch—from ringed discs and patterned blobs to lumpy ropes and wavy fronds. Taking to the warm shallow seas as early as 570 million years ago, these soft and squishy misfits were Earth's earliest complex life. 
 
 One of the most famous of the lot is Dickinsonia. This flattened, ribbed oval can grow over four feet across and sports a distinct ridge down its center. However, the question of what exactly Dickinsonia is has long puzzled scientists. At various points in history, they’ve assigned these curious forms to almost every kingdom of life. In recent decades, the debate has swirled around three groups: some researchers proposed fungi, others said protists, still others say animals. 
 
 In a new study, published this week in Science, researchers used modern techniques to take a fresh look at the ancient creatures. Their results join mounting evidence that suggests Dickinsonia is among the earliest animal life yet found—predating the Cambrian explosion of life, which took place 541 million years ago and marked the rise of most major animal groups still around today. 
 
 “This was already actually one of us,” says study author Jochen Brocks, paleobiogeochemist at Australian National University. “It was an animal.” Though Dickinsonia eventually went extinct, the animal is one of many early experiments in multicellular life that eventually gave rise to our modern menagerie. 
 
 “I think it sort of completes the puzzle in our understanding of Dickinsonia,” says Mary Droser, a paleontologist at University of California, Riverside, who was not involved in the work. 
 
 In the past few years, she explains, paleontologists largely reached a consensus that Dickinsonia was an animal, based on studies of its imprints. But the new work builds on this evidence, using chemistry to support the animal hypothesis. “This is really helping to put Dickinsonia as part of the story of animal evolution on planet Earth,” Droser says. 
 
 What Are the Ediacarans? 
 
 First discovered in 1946 in the Ediacara hills in the Flinders ranges of South Australia, these evolutionary oddballs bear only the vaguest resemblance to modern life-forms. Ediacarans are as “strange as life on another planet, but easier to reach,” described paleontologist Adolf Seilacher in a 2007 paper for the Geological Society of London, Special Publications. 
 
 Their appearance marks a shift from tiny to tremendous life as evolution tested out body plans of increasing size. More than 50 types of Ediacarans are now known, and they have been found on every continent, save for Antarctica. 
 
 By studying when big life burst onto the scene, scientists can better understand the makings of complex creatures. The work could also yield clues about how life arises on far-flung worlds. And compared to finagling research on other planets, “it's a lot cheaper to go back in time and look at how life unfolded on Earth,” Droser says. 
 
 How to Study What's Not There 
 
 One challenge in studying Ediacarans is the issue of preservation. Their squishy bodies have long since decayed away, and they lack bones or shells that would remain in the fossil record. This means most of these forms are only known from imprints or traces of the ancient inhabitants—many of their delicate features likely lost in the crude traces. The creatures are also very early members of the evolutionary tree, differing greatly from modern life-forms, which makes it difficult to assign them branches. In the 1980s, researchers even proposed Ediacarans should be their own extinct kingdom. 
 
 Past work has focused on physical analysis of Dickinsonia traces—growth and development, evidence of movement, size, and complexity. For new clues, in this latest study, scientists turned to molecular biomarkers known as sterols. Many critters make them, but they're slightly different for each group. 
 
 Animals make a version known as cholesterols, “like we find in chicken McNuggets,” Brocks jokes. But Ediacarans weren't chowing down on fried foods. These chemical compounds actually play an important role in the membranes of the cells of virtually all animals, helping to regulate what goes in and out. 
 
 Scientists have long used biomarker analysis to seek out algae in bulk sediments. “In this case, what you get is an average composition of the ecosystem that was living there,” explains Ilya Bobrovskiy, lead author of the new study and a PhD student at the Australian National University. 
 
 Dinosaurs 101 Over a thousand dinosaur species once roamed the Earth. Learn which ones were the largest and the smallest, what dinosaurs ate and how they behaved, as well as surprising facts about their extinction. 
 
 Because the Ediacaran bodies are largely imprints, no one had attempted to test for biomarkers of these ancient weirdos. However, some Ediacaran imprints still sport a thin layer of organic material. And Bobrovskiy thought that perhaps the carbonaceous bonds in this organic film hold the secrets to what these bizarre forms once were. 
 
 Brocks, Bobrovskiy’s graduate adviser, was skeptical. “I first thought it was a crazy idea,” he says. But not wanting to discourage his ambitious student, he gave the go-ahead. 
 
 What Did the Analysis Show? 
 
 Bobrovskiy developed a method to test for fossil sterols in the remnants of the Ediacarans, comparing the results to biomarkers extracted from the surrounding rock. 
 
 To test the method, Bobrovskiy first turned to the Ediacaran creature Beltanelliformis, once thought to be related to algae, fungus, or even jellyfish. The biomarkers instead pointed to it being spherical colonies of cyanobacteria. They published their analysis earlier this year in Nature Ecology and Evolution. 
 
 Then the team turned to Dickinsonia, collecting samples from the White Sea region of northwest Russia. 
 
 “The molecular composition of the fossil and the molecular composition from the seafloor around the fossil was black and white,” Brocks says. An abundance of ancient cholesterols—up to 93 percent—in the trace remains pointed to animal. Whereas the surrounding seafloor had very little, and instead contained what's known as ergosteroids, suggesting the presence of green algae. 
 
 The beautiful simplicity of the analysis is partly what makes this new work remarkable. “It's a very creative way to try to get at this question,” says Paula Welander, a microbiologist at Stanford University who was not involved in the study. “It's one of those things: Why didn't anyone think of doing it before?” 
 
 The method will likely be useful to help understand other enigmatic Ediacarans, says Renee Hoekzema, a palaeontologist and mathematician at the University of Oxford who was not part of the work, via email. She'd be particularly interested in chemical analysis of the plume-like rangeomorphs, which may be related to Dickinsonia. This is one of the forms Brocks and his group are targeting next. 
 
 "This is an exciting time," Hoekzema says. "After seventy years of debate we are starting to get a grip on the enigmatic nature of the Ediacara biota." 
 
 How Can Biomarkers Stick Around For So Long? 
 
 Over time, all organics break down. Cholesterol is no exception, Brocks notes. But the products of this decay are very specific, he explains, and “the original skeleton of the cholesterol” is still preserved in these molecular fossils. 
 
 Welander, who studies the creation and function of modern sterols to help better interpret ancient traces, praises the rigorousness of the work, noting the team “really dotted all their i's and crossed all their t's.” 
 
 Of course, nothing is ever certain in the world of science. The study is based on the assumption that only animals create cholesterols, which Welander notes is fair with the current data but has the potential to change as we learn more about the many forms of life on Earth. 
 
 “There's a lot of uncertainty,” Bobrovskiy says of studying such ancient life. “But applying biomarkers removes a large part of this uncertainty.” 
 
 Droser adds: “Coupled with everything else, it is really hard to argue that this wasn't an animal.” 
 
 Was Dickinsonia the First Animal Ever? 
 
 Though scientists can't say exactly when the first animal arose, ancient traces hint it was more than 600 million years ago. However, Dickinsonia, with its newly confirmed classification, falls among a group of the oldest animals yet found. Kimberella, an early mollusk-like animal, rivals Dickinsonia in age. So does the worm-like creature that likely left the winding tracks known as Helminthoidichnites. 
 
 Around 541 million years ago, squishy Ediacarans gave way to the fantastical critters of the Cambrian explosion, trussed up in their spikes and armor. ||||| Image copyright Ilya Bobrovskiy Image caption The affiliations of Dickinsonia had previously been unclear 
 
 Scientists have identified the earliest known animal in the geological record. 
 
 It's a 558-million-year-old oval-shaped creature that may have borne a superficial resemblance to a segmented jellyfish. 
 
 Researchers found specimens of the creature, known as Dickinsonia, that were so well preserved they still contained molecules of cholesterol. 
 
 This fat is a hallmark of animal life, the team reports in the journal Science. 
 
 Dickinsonia belongs to a group of life forms known as the Ediacaran biota. They were the first complex multi-cellular organisms to appear on Earth. 
 
 But they have been extremely difficult to classify, and their position on the tree of life has been one of the greatest mysteries in palaeontology. 
 
 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. 
 
 The new analysis of a specimen found in north-west Russia places Dickinsonia firmly within the animal kingdom. 
 
 Image copyright Ilya Bobrovskiy Image caption The fossils were unearthed at Zimnie Gory in the White Sea area of north-west Russia 
 
 Image copyright Ilya Bobrovskiy Image caption ANU researcher Ilya Bobrovskiy found specimens of Dickinsonia and a related organism called Andiva in the rocks 
 
 "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," said co-author Jochen Brocks, an associate professor at the Australian National University (ANU) in Canberra. 
 
 "Scientists have been fighting for more than 75 years over what Dickinsonia and other bizarre fossils of the Ediacaran Biota were," he explained, adding: "The fossil fat now confirms Dickinsonia as the oldest known animal fossil, solving a decades-old mystery that has been the Holy Grail of palaeontology." 
 
 The Ediacaran biota appeared around 600 million years ago, and flourished for tens of millions of years before the event called the Cambrian explosion. 
 
 This massive diversification of life occurred around 541 million years ago; it's when most of the major animal groups appear in the fossil record. 
 
 The Ediacaran species largely disappear when the Cambrian explosion happens. As such, they straddle an ancient age when the Earth was dominated by bacteria and a later age of dominance by animals. 
 
 Image copyright Ilya Bobrovskiy Image caption Analysis of organic matter preserved in the Dickinsonia fossils placed the creature firmly within the animal kingdom 
 
 Most multicellular life leaves behind stable molecules called sterane hydrocarbons which can be preserved in sediments for millions of years. The molecular structures and abundances of these compounds can be specific to particular types of organism. 
 
 Team member Ilya Bobrovskiy, from ANU, extracted and analysed molecules from inside the fossil. 
 
 He found that Dickinsonia fossils contained very high levels of cholesterol molecules - up to 93% - compared with the surrounding sediment, where levels were roughly 11%. 
 
 Furthermore, the fossils lacked the types of stable molecules that are sometimes left behind by fungi. 
 
 "The problem that we had to overcome was finding Dickinsonia fossils that retained some organic matter," said Ilya Bobrovskiy. 
 
 "Most rocks containing these fossils, such as those from the Ediacara Hills in Australia, have endured a lot of heat, a lot of pressure, and then they were weathered after that - these are the rocks that palaeontologists studied for many decades, which explained why they were stuck on the question of Dickinsonia's true identity." 
 
 Follow Paul on Twitter. ||||| Dickinsonia fossil. Credit: The Australian National University (ANU) Scientists from The Australian National University (ANU) and overseas have discovered molecules of fat in an ancient fossil to reveal the earliest confirmed animal in the geological record that lived on Earth 558 million years ago. 
 
 The strange creature called Dickinsonia, which grew up to 1.4 metres in length and was oval shaped with rib-like segments running along its body, was part of the Ediacara Biota that lived on Earth 20 million years prior to the 'Cambrian explosion' of modern animal life. 
 
 ANU Ph.D. scholar Ilya Bobrovskiy discovered a Dickinsonia fossil so well preserved in a remote area near the White Sea in the northwest of Russia that the tissue still contained molecules of cholesterol, a type of fat that is the hallmark of animal life. 
 
 Lead senior researcher Associate Professor Jochen Brocks said the 'Cambrian explosion' was when complex animals and other macroscopic organisms—such as molluscs, worms, arthropods and sponges—began to dominate the fossil record. 
 
 "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," said Associate Professor Jochen Brocks from the ANU Research School of Earth Sciences. 
 
 "Scientists have been fighting for more than 75 years over what Dickinsonia and other bizarre fossils of the Edicaran Biota were: giant single-celled amoeba, lichen, failed experiments of evolution or the earliest animals on Earth. The fossil fat now confirms Dickinsonia as the oldest known animal fossil, solving a decades-old mystery that has been the Holy Grail of palaeontology." 
 
 Mr Bobrovskiy said the team developed a new approach to study Dickinsonia fossils, which hold the key between the old world dominated by bacteria and the world of large animals that emerged 540 million years ago during the 'Cambrian explosion'. 
 
 "The problem that we had to overcome was finding Dickinsonia fossils that retained some organic matter," said Mr Bobrovskiy from the ANU Research School of Earth Sciences. 
 
 "Most rocks containing these fossils such as those from the Ediacara Hills in Australia have endured a lot of heat, a lot of pressure, and then they were weathered after that—these are the rocks that palaeontologists studied for many decades, which explained why they were stuck on the question of Dickinsonia's true identity." 
 
 Palaeontologists normally study the structure of fossils, but Mr Bobrovskiy extracted and analysed molecules from inside the Dickinsonia fossil found in ancient rocks in Russia to make the breakthrough discovery. 
 
 "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," Mr Bobrovskiy said. 
 
 "These fossils were located in the middle of cliffs of the White Sea that are 60 to 100 metres 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." 
 
 Scientists from The Australian National University (ANU) have discovered molecules of fat in an ancient fossil to reveal the earliest confirmed animal in the geological record that lived on Earth 558 million years ago. Credit: The Australian National University 
 
 Associate Professor Brocks said being able to study molecules from these ancient organisms was a gamechanger. 
 
 "When Ilya showed me the results, I just couldn't believe it," he said. 
 
 "But I also immediately saw the significance." 
 
 ANU led the research in collaboration with scientists from the Russian Academy of Science and the Max Planck Institute for Biogeochemistry and the University of Bremen in Germany. 
 
 The research is published in Science. 
 
 Explore further: Earth's oldest animals formed complex ecological communities 
 
 More information: I. Bobrovskiy el al., "Ancient steroids establish the Ediacaran fossil Dickinsonia as one of the earliest animals," Science (2018). science.sciencemag.org/cgi/doi … 1126/science.aat7228 
 
 R.E. Summons el al., "Chemical clues to the earliest animal fossils," Science (2018). science.sciencemag.org/cgi/doi … 1126/science.aau9710 
 

– A researcher calls it "a decades-old mystery that has been the Holy Grail of paleontology": What, exactly, Dickinsonia was. It's one of a group of lifeforms called the Ediacaran biota, which the BBC describes as the "first complex multi-cellular organisms to appear on Earth." But for decades they've defied definitive classification, with scientists suggesting they could be everything from lichen to giant single-celled amoeba to "evolutionary dead-ends." Now, an answer: Dickinsonia is an animal that dates back 558 million years, making it the earliest confirmed one in the geological record. That conclusion comes thanks to fat, reports Phys.org. Ilya Bobrovskiy of Australian National University discovered a Dickinsonia fossil in 300-foot-high cliffs along the White Sea in northwest Russia, in a place so remote she reached it via helicopter. The fossil was superbly preserved, so much so that its tissue had cholesterol molecules present in it. "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," says ANU professor Jochen Brocks, co-author of the paper on the discovery, which was published in Science. The Cambrian explosion that gave rise to modern animal groups didn't happen for another 20 million years or so. As for the oval Dickinsonia's appearance, the BBC describes it as possibly bearing "a superficial resemblance to a segmented jellyfish." National Geographic delves into the difficulty of studying Ediacarans, who had no shells or bones to leave behind and whose "squishy bodies have long since decayed." Read more on how the team overcame that here.