Ediacaran fossils reveal origins of biomineralization that led to expansion of life on Earth

Life on Earth began from a single-celled microbe, while the rise to the multicellular world in which we live arose due a vital chemical process known as biomineralization, during which living organisms produce hardened mineralized ...
Fossil skeletons of cloudinids (Cloudina), tubular structures comprised of carbonate cones up to ~1.5cm in length, have been found in Tsau Khaeb National Park, Namibia, dating back to 551–550 million years ago in the Ediacaran (~635–538 million years ago). Dr. Fred Bowyer, from the University of Edinburgh, and colleagues aimed to use these fossils to define the location, timing and reason for why biomineralization initiated on Earth and the magnitude of its impact.

New research published in Earth and Planetary Science Letters combines sediment analysis with geochemical data in the form of carbon and (the same element with different atomic masses) from limestones in the Kliphoek Member, Nama Group. The research team suggest this rock was once deposited in a during a lowstand before a period of transition to open marine conditions.
The Nama Group of rocks are considered some of the most important for understanding the radiation of life on Earth into the Cambrian (~538–485 million years ago), colloquially termed the "Biological Big Bang."

During fieldwork in Namibia, the bedding planes between successive rock units reveal the wonders of life's history through ichnofossils, the traces of ancient activity but not expressly preserving the organism's remains. Dr Bowyer suggests these are structures created by soft-bodied microbes, occurring in the lower part of the study site (Mara Member) prior to biocalcification. Above this, the research team began to see the first signs of Cloudina in the Kliphoek Member, distinctive conical fossils with cone structures nested within each other.

Summarized occurrence of known soft-bodied and skeletonised fossils through the Ediacaran, with the onset of biomineralisation supported by Cloudina. Credit: Bowyer et al, 2023.
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Cloudina fossils preserved in the Kliphoek Member of the Tsau Khaeb National Park, Namibia. Credit: Bowyer et al, 2023.
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Schematic interpretation of depositional environments across the study area in Tsau Khaeb National Park, Namibia, during which Cloudina biomineralisation occurred. A) Marine transgression led to deposition of sandstones and siltstones in a shallow shoreface; b) continued marine transgression forming an evaporite basin partially restricted from the open ocean; c) peak sea level with open marine conditions and extensive carbonate deposits; d) sea level fall during which Cloudina biomineralisation occurred in periods of oxygenation. Credit: Bowyer et al, 2023.
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