The Ediacaran is a period in Earth’s history that spans from -635 to -541 million years. Its name refers to the hills of Ediacara where the earliest animal fossils on Earth were found, dating back to 600 to 580 million years ago. Fossils from the same period were recently discovered in the Doshantuo Formation in southern China, confirming the first episode of a biodiversity explosion across the planet.
a mysterious fall
Some rare fossil records nonetheless report a decline in biodiversity by -550 million years ago, which some authors believe reflects an environmental crisis that caused the first mass extinctions on Earth. To assess the reality of such an event during the Ediacaran, researchers from the University of Cambridge analyzed the composition of three communities of fossils that cover the last 32 million years of this geologic period, i.e. 575 and 543 million years. are old. The oldest, Avalon Assembly (-575 to -565 million years) is known from deposits discovered in deep waters off the coast of Canada. Fossils, essentially rangeomorphs, are relatively simple with limited ecological and morphological diversity.
Rangeomorphs looked like fern-like species that were (mostly) about ten centimeters long and some of which reached two meters. Credit : Jennifer Hoyal Kuthil.
The second community, the White Sea Assemblage (-558 to -550 million years ago), consists of fossils found on the ocean floor of southern Australia along with a dominant animal: dickinsonia, A Like the flat oval equipped with a central dorsal that lived on the ocean floor without a mouth, neither intestine, nor anus! Yet it also includes many other fossils with many different forms and ecotypes. Finally, the third community studied comes from Namibia, the Nama assemblage (-549 to -543 million years ago) that contains the oldest bio-mineral fossils, but also reports a decline in biodiversity, which is approximately – It is consistent with an extinction episode 550 million years ago. ,
the spark that ignited the Cambrian explosion
The scientists used published Palaeolithic data, such as ocean depth and reef characteristics, to analyze the interactions between species in each community and each’s expertise in relation to its environment. Their results, published in the journal plus biologyprompt The increasingly complex community structure in fossil assemblages suggests that species were becoming more specialized and engaging in more interactions. This, according to the researchers, suggests competitive exclusion rather than mass extinction as the cause of the decline in biodiversity at the end of the Ediacaran. At that time, those life forms that had disappeared without leaving any lineage had already developed characteristics. Usually associated with the Cambrian explosion.
Emily Mitchell Laser Scanning Surface E, Mistaken Point Reserve. In the foreground, Ediacaran organisms such as Fructophusus are visible. Credit : Charlotte G. kenchington,
University of Cambridge’s Emily G. To Michelle: “Ediacaran is the spark that ignited the Cambrian explosion“. This Cambrian radiation explosion saw the appearance of some of the most astonishing fossils ever discovered. A single location, Mount Burgess (Canada), provides one of the best vantage points of this period of dramatic evolutionary change and experimentation. made up of most of the major groups of modern animals.