Cambrian Explosion: trying to remove the gap (Introduction)

by David Turell , Tuesday, March 26, 2019, 00:54 (2070 days ago) @ David Turell

Another transparent attempt:

https://cosmosmagazine.com/palaeontology/inside-out-ediacaran-fossils-might-represent-i...

"The Ediacarans are weird-looking things. Estimated to be over 560 million years old, they offer the best answer to Darwin’s dilemma: what preceded the Cambrian explosion which spawned the prototypes of most modern animals 541 million year ago?

"But Ediacaran organisms, the ancient fossils of which have been found worldwide, throw up their own dilemmas. For one, what exactly were they? Some resemble plants but aren’t because they lived in seas too deep to access light; others have a trifold symmetry that doesn’t exist anymore. But some were bilaterally symmetrical and these are the best candidates for prototypes of today’s animals.

"But beyond Darwin’s dilemma lies another one – more mundane, but no less pressing to scientists.

"Ediciacarans were soft bodied, evidenced by the fact that fossils depict them folded over or with bits torn off. How then did they fossilise? They aren’t like trilobites or dinosaur bones.
Rather than petrified 3D replicas of the original, they are impressions stamped into sandstone.

***

"Now palaeontologist Ilya Bobrovskiy from the Australian National University (ANU) and colleagues have come up with a new explanation. No death masks are required, they say. Rather, they propose in an article in the journal Nature Ecology and Evolution, the flow properties, or rheology, of different sediments could explain the imprints.

“'It’s a welcome addition,” says Guy Narbonne, a palaeontologist from Queens University in Canada, who works on Ediacaran sites in Newfoundland, “but it does not necessarily do away with other models.”

"The death mask theory to explain Ediacaran impression fossils holds up well for places such as Australia’s Flinders Ranges – where the fossils were first discovered in 1947 at a site called Ediacara Hills – and Mistaken Point in Newfoundland.

***

"When it comes to the mechanism of preservation at the White Sea, “it’s been a blank”, says Narbonne, “I think this paper is important, arguing that the prevailing preservation mechanisms are not part of the equation.”

"He adds, though: “It doesn’t eliminate other possibilities. Like all good science, it raises nearly as many questions as it answers.”

"For Jim Gehling, a palaeontologist at the South Australian Museum and expert on the Flinders Ranges Ediacarans, the theory “fails to explain the vast array of photographed and cast specimens of Dickinsonia fossils that include evidence of torn specimens, folded over specimens and serial ‘resting traces’ — regarded as evidence of staged movement.”

"Palaeontologist Alex Liu from Cambridge University, UK, sees a middle path. “I think that the most likely scenario is that both early cementation and the effects of rheology acted in combination to preserve Ediacaran fossils in the Flinders and elsewhere,” he says."

Comment: The Ediacaran fossils that are found do not show internal organs and this study blames that on the methods of fossilization. The approach seems to be: If there were organs, perhaps the Cambrian gap isn't so big? That ignores the vast phenotypic changes in the Cambrian. Among Darwinists hope springs eternal.