Gorgeous spider fossils lead to a quick hunt for incredibly well-preserved specimens

A fossilized spider from the Aix-en-Provence Formation, France, seen on a hand specimen covered with a fluorescent microgram from the same fossil. Under normal lighting, a spider fossil is difficult to distinguish from the matrix of surrounding rocks, but when the fossil is excited with ultraviolet light, its chemical makeup causes it to glow brightly, revealing additional details of its preservation. Credit: Olcott et al.

Glowing spiders’ fossils have led to a paranormal study of how they were preserved in Aix-en-Provence.

A geological formation near Aix-en-Provence, France, is famous as one of the world’s most important treasures of Cenozoic fossil species. Scientists have discovered exceptionally well-preserved fossilized plants and animals since the late 18th century.

“Most of life does not become a fossil.” – Alison Olcott

The Aix-en-Provence Formation is particularly famous for fossilized terrestrial arthropods from the Oligocene period (about 23-34 million years ago). Since arthropods – animals with exoskeletons like spiders – are rarely fossilized, their abundance in Aix-en-Provence is impressive.

A new study published in the journal Earth and Environment Communications On April 21, 2022, researchers at the University of Kansas were the first to ask: What unique chemical and geological processes in Aix-en-Provence make the spiders of the Oligocene period so fascinating?

“Most life doesn’t turn into a fossil,” said lead author Alison Olcott, associate professor of geology and director of the Kuwait University Research Center. “It’s hard to become a fossil. You have to die under very specific conditions, and one of the easiest ways to become a fossil is to have hard parts like bones, horns, and teeth. Life, like spiders, is irregular – but we have exceptional preservation periods when all conditions are in harmony for conservation to occur. .

Scanning an electronic image of the fossilized spider’s abdomen reveals the presence of a black polymer in the fossil and the presence of two types of microalgae: a mat of erect diatoms in the fossils and centrioles scattered in the surrounding matrix. This image is covered with chemical maps of sulfur (yellow) and silica (pink) revealing that while the microalgae is siliceous, the polymer covering the fossil is rich in sulfur. Credit: Olcott et al.

Olcott and his co-authors at KU Matthew Downen—then a doctoral student in the Department of Geology and now associate director of the University Research Center—and Paul Selden, KU Distinguished Professor Emeritus, along with James Schiffbauer of the University of Missouri. Discover the exact processes in Aix-en-Provence that provided a pathway for the preservation of spider fossils.

“Matt was working on describing these fossils and we decided – on a whim – to put them under a fluorescent microscope to see what happened,” Olcott said. “To our surprise, it glowed, so we were very interested in what makes the chemistry of these fossils shine. If you look at the fossil in the rock, you’ll see that it’s almost indistinguishable from the rock itself, but it glows a different color under the fluorescent strip. So we set out to explore the chemistry and found that the fossils themselves It contains a black polymer made of carbon and sulfur, which, under a microscope, is similar to the tar you see on the road. We also noticed that there were thousands and thousands and thousands of microalgae in all of the fossils and covering the fossils themselves.”

Fossil Aix-en-Provence spider with diatoms

Spider fossil from the Aix-en-Provence formation with a white square indicating the location of the scanning electron microscope image and a chemical map of sulfur (yellow) and silica (pink) in the upper left corner. Together they reveal a black sulfur-rich polymer in the fossil and the presence of two types of siliceous microalgae: a mat of erect diatoms in the fossil and centriolar diatoms dispersed in the surrounding matrix. Credit: Olcott et al.

Olcott and his colleagues hypothesize that the extracellular substance produced by these microalgae, called diatoms, could shield spiders from oxygen and increase their sulfur content, a chemical change that explains the preservation of fossils as carbon membranes for the next millions of years.

“These microalgae make a sticky, sticky ball – that’s how they stick together,” said the KU researcher. “I hypothesized that the chemistry of these microalgae and the substances they emit made it possible for this chemical reaction to preserve spiders. Essentially, the chemistry of the microalgae and the chemistry of the spider work together to achieve this unique conservation.” “

In fact, this phenomenon of sulfur is the same common industrial process used to preserve rubber.

“Vulcanization is a natural process — we do it ourselves to treat rubber in a known process,” Olcott said. “Sulfur takes the carbon and binds it to the sulfur and fixes the carbon, which is why we do it with rubber so it lasts longer. What I think happened here chemically is that the exoskeleton of the spider is chitin, which is a long polymer with adjacent carbon units, which is an ideal environment. for sulfur bridges to step in and really stabilize things.”

The presence of diatomic mats likely serve as evidence that better-preserved fossil deposits will be found in the future, Olcott said.

“The next step is to extend these techniques to other sediments to see if conservation is associated with diatom mats,” she said. “Out of all the other exceptional fossil conservation sites in the world in the Cenozoic Era, nearly 80 percent of them have been found with this microalgae. So we wonder if this explains most of the fossil sites we have now — primarily shortly after The extinction of the dinosaurs So far, this mechanism may be responsible for providing us with information to explore the evolution of insects and other terrestrial life after the dinosaurs and to understand the climate change because there is a period of rapid climate change and these terrestrial organisms help us understand what happened to life the last time the climate began to change.”

Olcott and colleagues were the first to analyze conservation chemistry in Aix-en-Provence, a fact they attribute in part to the challenges of applying science during Categories Science and technology

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