Why The Weird Ediacara Fauna Didn’t Survive Earth’s First Known Mass Extinction

Science Why The Weird Ediacara Fauna Didn’t Survive Earth’s First Known Mass Extinction David Bressan Contributor Opinions expressed by Forbes Contributors are their own. I deal with the rocky road to our modern understanding of earth Following New! Follow this author to stay notified about their latest stories. Got it! Nov 8, 2022, 08:42am EST | New! Click on the conversation bubble to join the conversation Got it! Share to Facebook Share to Twitter Share to Linkedin Tribrachidium heraldicum, one of the most enigmatic critters from the Ediacara fauna.

D. Bressan A new study by Virginia Tech geobiologists traces the cause of the first known mass extinction of animals to decreased global oxygen availability, leading to the loss of about 80 percent of animals present 500 million years ago. In 1947, geologist Reginald C.

Sprigg announced the discovery of large fossils from the Ediacara Hills in Australia. Dating of the rock formations revealed that the Ediacara fauna was more than 550 million years old, quite a sensation at the time, as nobody expected multicellular life to appear so early in Earth’s history. The Ediacara fauna includes many weird organisms of unknown affinity, like Dickinsonia , an egg-shaped, segmented hybrid between a worm and a jellyfish, Charnia , a segmented and branched organism resembling superficially modern sea pens, or Tribrachidium , showing a threefold rotational symmetry not found in any modern animal.

“These organisms occur so early in the evolutionary history of animals that in many cases they appear to be experimenting with different ways to build large, sometimes mobile, multicellular bodies,” Scott Evans , a postdoctoral researcher in the Department of Geosciences at Virginia Tech College of Science, explains. Ruling the shallow sea for roughly 96 million years, the Ediacara fauna went extinct about 539 to 500 million years ago, marking the end of the Proterozoic Eon and the beginning of the Phanerozoic Eon – the time in Earth’s history ruled by “modern animals. ” MORE FOR YOU Why The Rock’s Social Media Muscle Made Him Hollywood’s Highest-Paid Actor The Best Bath Towels To Upgrade Your Bathing Experience Report Affirms More Housing Means Lower Rents And Prices “Essentially, this extinction may have helped pave the way for the evolution of animals as we know them,” so Evans.

In a new study, Evans and collagues – limited by the COVID-19 pandemic in doing field work outside – put together a global database based mostly on published records to test ideas about changing diversity at the end of the Proterozoic. “This included the loss of many different types of animals, however those whose body plans and behaviors indicate that they relied on significant amounts of oxygen seem to have been hit particularly hard,” Evans explains. “This suggests that the extinction event was environmentally controlled.

” All members of the Ediacara fauna lack any evidence of external organs, like gills or even a mouth. Likely they adsorbed oxygen and nutrients directly from the water through their body surface. But this adaption made them vulnerable to low oxygen levels.

“Environmental changes, such as global warming and deoxygenation events, can lead to massive extinction of animals and profound disruption and reorganization of the ecosystem,” said Shuhai Xiao , co-author and professor in the Department of Geosciences. “This has been demonstrated repeatedly in the study of Earth history, including this work on the first extinction documented in the fossil record. This study thus informs us about the long-term impact of current environmental changes on the biosphere.

” What exactly caused the drop in global oxygen ? That’s still up for debate. “The short answer to how this happened is we don’t really know,” Evans said. “It could be any number and combination of volcanic eruptions, tectonic plate motion, an asteroid impact, etc.

, but what we see is that the animals that go extinct seem to be responding to decreased global oxygen availability. ” The study by Evans and Xiao is timelier than one would think. In an unconnected study, Virginia Tech scientists recently found that anoxia, the loss of oxygen availability, is affecting the world’s fresh waters .

The cause? The warming of waters brought on by climate change and excess pollutant runoff from land use. Warming waters diminish fresh water’s capacity to hold oxygen, while the breakdown of nutrients in runoff by freshwater microbes gobbles up oxygen. “Our study shows that, as with all other mass extinctions in Earth’s past, this new, first mass extinction of animals was caused by major climate change – another in a long list of cautionary tales demonstrating the dangers of our current climate crisis for animal life,” concludes Evans.

The paper ” Environmental drivers of the first major animal extinction across the Ediacaran White Sea-Nama transition ” is published in the Proceedings of the National Academy of Sciences (2022). Material provided by Virginia Tech . David Bressan Editorial Standards Print Reprints & Permissions.