Tuesday 21 October, 2014

Nursery of ‘earliest ever animals’ found buried under Pompeii-style ash

Published On: Tue, Jul 10th, 2012 | Geology | By BioNews

A Pompeii style ash eruption in Canada that buried some of the earliest animal lifeforms more than 579 million years ago has been discovered.

A team from the Universities of Oxford and Cambridge, in collaboration with the Memorial University of Newfoundland, discovered over 100 fossils of what are believed to be “baby” rangeomorphs – frond-shaped organisms which lived about 580-550 million years ago.

The “creatures” superficially resemble sea-pen corals but, on closer inspection, are unlike any animals that are alive today.

This “nursery” of baby rangeomorphs had been found in rocks at the Mistaken Point Ecological Reserve in Newfoundland, Canada.

The teams had been looking for evidence of life from the mysterious Ediacaran period (635-542 million years ago) in which the first “animals” – complex multicellular organisms had appeared.

The fossil remains of rangeomorphs are often described as “fern-like” and it is unclear where exactly they fit in the tree of life.

Because they lived deep beneath the ocean where there was no light they are not thought to be plants but they may not have had all of the characteristics of animals.

Mysteriously, their frond-shaped body-plan, which might have helped them gather oxygen or food, did not survive into the Cambrian period (542-488 million years ago).

“The fossilised ‘babies’ we found are all less than three centimetres long and are often as small as six millimetres; many times smaller than the ‘parent’ forms, seen in neighbouring areas, which can reach up to two metres in length,” the Daily Mail quoted Professor Martin Brasier of Oxford University’s Department of Earth Sciences, one of the authors of the report, as saying.

“This new discovery comes from the very bottom of the fossil-bearing rocks, making it one of the oldest bedding planes to preserve ‘animal’ fossils in the whole of the geological record.

“We think that, around 579 million years ago, an underwater ‘nursery’ of baby Ediacaran fronds was overwhelmed, Pompeii-style, by an ash fall from a volcanic eruption on a nearby island that smothered and preserved them for posterity,” he added.

Dr Alexander Liu of Cambridge University’s Department of Earth Sciences, an author of the report, said that the juveniles had been exceptionally well preserved, and included species that had never before found in rocks of this age, which increased the known taxonomic diversity of the earliest Ediacaran fossil sites.

“The discovery confirms a remarkable variety of rangeomorph fossil forms so early in their evolutionary history,” Liu said.

The finding reinforced the idea that “life got large” around 580 million years ago, with the advent of these frond-like forms, some of which grew up – in better times – to reach almost two metres in length.

“We are now exploring even further back in time to try and discover exactly when these mysterious organisms first appeared and learn more about the processes that led to their diversification in an ‘Ediacaran explosion’ that may have mirrored the profusion of new life forms we see in the Cambrian,” Brasier said.

The research will be published in the Journal of the Geological Society.

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