A new study questions the mass extinction of the Ediacaran fauna before the Cambrian explosion

The first animals formed complex ecological communities more than 550 million years ago, laying the evolutionary groundwork for the Cambrian explosion, according to a study by Rebecca Eden, Emily Mitchell and colleagues at the University of Cambridge, UK, published in the open access journal PLOS Biology .

The first animals evolved towards the end of the Ediacaran period, about 580 million years ago. However, the fossil record shows that, after an initial boom, diversity declined in the run-up to the spectacular burst of biodiversity in the so-called Cambrian explosion , almost 40 million years later.

Scientists have suggested that this decline in diversity is evidence of a mass extinction event of the Ediacaran fauna around 550 million years ago - possibly caused by an environmental catastrophe - but previous research has not studied the structure of these ancient ecological communities.

To assess the evidence for a mass extinction in the Ediacaran period, the researchers analyzed the metacommunity structure of three fossil assemblages spanning the last 32 million years of this geological period (between 575 and 543 million years ago). They used published paleoenvironmental data, such as ocean depth and rock characteristics, to search for metacommunity structure, indicative of environmental specialization and interactions between species.

The analysis revealed an increasingly complex community structure in the latest fossil assemblages, suggesting that species were becoming more specialized and engaging in more interspecies interactions toward the end of the Ediacaran era, a trend often seen during the Ediacaran era. ecological succession.

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