Prior to the Cambrian Explosion, the First Creatures Evolved Sophisticated Habitats

Early species formed complex ecological systems more than 550 million years ago, setting the developmental phase for such Cambrian explosion.

Around 580 million years ago, towards the conclusion of the Ediacaran epoch, the first creatures appeared, as per ScienceDaily. 

The animals in the Ediacaran Period

(Photo : SAM YEH/AFP via Getty Images)

The fossil record, on the other hand, demonstrates that after an initial burst, diversity fell in the lead-up to the rapid growth of biodiversity in the so-called "Cambrian explosion" approximately 40 million years later.

Scientists believe this decline in variety is indicative of a large extinction event around 550 million years ago, likely triggered by an environmental disaster, but the previous study has not looked into the organization of these ancient biological groups.

Researchers examined the metacommunity structure of three fossil assemblages from the past 32 million years of the Ediacaran epoch to assess the evidence for an Ediacaran mass extinction (between 575 to 543 million years ago).

They looked for a metacommunity structure suggestive of ecological specializations and relationships between species using existing paleoenvironmental data such as ocean depth and rock features.

The research found increasingly complicated structure and function in the later fossil ensembles, implying that species became more specialized and engaged in more inter-species relationships towards the end of the Ediacaran epoch, a common pattern throughout ecological succession.

According to the authors, the findings suggest competitive exclusion rather than mass extinction as the source of the late Ediacaran diversity reduction.

The research shows that the first animal communities in the late Ediacaran established elements of ecological and evolutionary dynamics often associated with the Cambrian boom, such as specialization and niche contraction.

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Ediacaran Period

The Ediacaran Period, also known as the Vendian Period, was the topmost division of the Proterozoic Eon of Precambrian chronology and the last of the three eras of the Neoproterozoic Era, spanning roughly 635 million to 541 million years ago.

The Ediacaran Period followed the Cryogenian Period (roughly 720 million to approximately 635 million years ago) and was replaced by the Cambrian Period's Fortunian Age (541 million to approximately 529 million years ago) (541 million to 485.4 million years ago), as per Britannica.

The Ediacaran Period yielded some of the first known evidence of the development of multicellular creatures (the metazoans).

The dominant Ediacaran fauna in the fossil evidence is a community of unconventional soft-bodied (invertebrate) forms that predated the Cambrian explosion-the unprecedented rise of life forms between 541 million and estimated 530 million years ago that included members of very many major phyla still extant today.

The Ediacaran Period began around 635 million years ago, coinciding with the accelerated retreat of ice sheets and glaciers affiliated with the Marinoan (or Varanger-Marinoan) glaciation, which began near the end of the Cryogenian Period and ended around 635 million years ago, and declines in the carbon isotope composition of marine rocks.

Oxygen levels in the atmosphere and seas increased, and many scientists believe that the shift in carbon isotopes may be linked to dissolved organic carbon oxidation in marine habitats.

However, the end of the Ediacaran Period was identified by a biological marker, the lowermost limit of the trace fossil Trichophycus pedum.

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