Juvenile example of the rangeomorph fossil Charnia, measuring just 17 millimetres in length. Note the fine detail of the branches. Credit: OU/Jack Matthews
Researchers have discovered the strange shapes of the world’s earliest-known baby animals preserved as fossils in rocks in Newfoundland, Canada, thanks to a Pompeii-style volcanic eruption more than a half-billion years ago.
The Pompeii-like deluge of ash preserved over 100 fossils of what are believed to be ‘baby’ rangeomorphs. These are bizarre frond-shaped organisms which lived 580-550 million years ago and superficially resemble sea-pen corals. On closer inspection, they are unlike any creature alive today.
Because they lived deep beneath the ocean where there would have been no light, the rangeomorphs are not thought to be plants although 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, does not survive into the Cambrian period (542-488 million years ago).
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“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,” Martin Brasier of Oxford University’s Department of Earth Sciences, said.
Braiser and colleagues from the Universities of Oxford and Cambridge, and the Memorial University of Newfoundland, detailed their findings in the current issue of the Journal of the Geological Society.
Exceptionally well preserved, the fossilized babies include species never before found in rocks from the mysterious Ediacaran period (635-542 million years ago) in which the first ‘animals’ — complex multicellular organisms — appeared.
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“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,” Brasier said.
The find reinforces 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.
Alexander Liu, Martin Brasier, Jack Matthews and Duncan McIlroy. A new assemblage of juvenile Ediacaran fronds from the Drook Formation, Newfoundland. Journal of the Geological Society, July 2012