POTENTIAL DIATOM-INFLUENCED FOSSIL PRESERVATION PATHWAY ACROSS THE CENOZOIC (Invited Presentation)

Sites of exceptional fossil preservation are responsible for much of our understanding of the history of life on Earth; most fossil localities only preserve the species with mineralized body parts (e.g., teeth, bones, and shells), which comprise about 15% of the species found within a particular ecosystem, while Fossil Lagerstätten can capture a much more complete record of an ecosystem by preserving soft-bodied organisms. However, without an understanding of the mechanisms that allowed for such remarkable fossilization, including any biases introduced by the preservation mechanism, we cannot reliably interpret the information preserved within these snapshots of ancient biotas.

One such remarkable fossil deposit is the Aix-en-Provence Formation, an Oligocene (22.5 Ma) Lagerstätte in southern France that contains an abundance of soft-bodied fossils preserved in exceptional detail. Many taxa have been described from this formation, including insects, spiders, fishes, and plants, suggesting a diverse ecosystem in a subtropical, brackish, lacustrine paleoenvironment. We used microscopy and chemical analysis of spiders found in the Oligocene Aix-en-Provence Formation to unravel the taphonomic pathway responsible for the preservation of these arachnids: the extracellular polymeric substances (EPS) produced by the diatoms found widely in this deposit could have helped promote the sulfurization of the spiders. Examination of similar Fossil-Lagerstätten reveals that this preservation pathway may be widespread across the Cenozoic and, if so, would be responsible for much of our understanding of insect, arachnid, amphibian, and plant life preserved in lacustrine settings.