Study: Animals developed complex ecosystems 550 million years ago

By Mark Waghorn via SWNS

The first animals developed complex ecosystems more than 550 million years ago, according to new research.

They looked nothing like we would recognize today - resembling giant leafy ferns, cabbages and even shapeless sacs.

Some bore a striking similarity to thin, quilted pillows - while others mirrored enormous corals called sea pens because they are shaped like quills.

But the "lost world" of primitive lifeforms herald a watershed moment in the history of Earth - laying the foundations for the Cambrian Explosion.

It was the period some 541 million years ago which saw the sudden appearance in the fossil record of creatures exhibiting recognizable body parts.

They included fins, legs, shells and skeletons. Most of the ancestors of modern animals can be traced to this point.

Lead author Dr. Emily Mitchell said: "We found the factors behind that explosion, namely community complexity and niche adaptation, actually started during the Ediacaran, much earlier than previously thought."

She added: "The Ediacaran was the fuse that lit the Cambrian explosion."

Ediacaran fossils are soft bodied and squidgy. The ability to form shells or skeletons did not evolve until it ended.

Dr. Mitchell explained: "The first animals evolved towards the end of the Ediacaran period, around 580 million years ago.

"However, the fossil record shows that after an initial boom, diversity declined in the run-up to the dramatic burgeoning of biodiversity in the so-called 'Cambrian explosion' nearly 40 million years later."

Scientists have suggested it is evidence of a mass extinction roughly 550 million years ago – possibly caused by an environmental catastrophe.

Some blame a steep decline in dissolved oxygen in the ocean. Others believe these early macroscopic animals were outcompeted by newly evolved rivals.

The study in PLOS Biology sheds fresh light on this enigmatic eon by investigating the structure of these ancient groups.

It suggests succession - rather than mass extinction - was behind the mysterious phenomenon.

Dr. Mitchell said: "Early animals formed complex ecological communities more than 550 million years ago, setting the evolutionary stage for the Cambrian explosion."

The University of Cambridge team analyzed the "metacommunity" of multiple, interacting species from three fossil assemblages.

They spanned the last 32 million years of the Ediacaran between 575 to 543 million years ago.

Environmental data such as ocean depth and rock characteristics discovered they connected and communicated with each other.

Dr. Mitchell said: "The analysis revealed increasingly complex community structure in the later fossil assemblages.

"It suggests species were becoming more specialized and engaging in more inter-species interactions towards the end of the Ediacaran era, a trend often seen during ecological succession."

The results point to competitive exclusion as the cause of the diversity drop at the end of the Ediacaran.

Added Dr Mitchell: "It indicates the features of ecological and evolutionary dynamics commonly associated with the Cambrian explosion - such as specialization and niche contraction - were established by the first animal communities in the late Ediacaran."

Their bizarre body plans have long baffled experts, who have struggled to place the creatures in the tree of life.

It was once thought they were all jellyfish. Only in the last two decades has it been established they represented a variety of long extinct animals.

They thrived across the world. Locations where remains have been discovered include Russia, Australia, Namibia and China.

But they vanished almost as suddenly as they arrived - disappearing from the fossil record within 30 million years.