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Why did the Ediacarans go extinct?

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images of Ediacaran fronds (635-541 mya)/Jennifer Hoyal Cuthill

New research suggests that Cambrian conditions may have done them in.

From ScienceDaily:

Rangeomorphs were some of the earliest large organisms on Earth, existing during a time when most other forms of life were microscopic in size. Most rangeomorphs were about 10 centimetres high, although some were up to two metres in height.

These creatures were ocean dwellers which lived during the Ediacaran period, between 635 and 541 million years ago. Their bodies were made up of soft branches, each with many smaller side branches, forming a geometric shape known as a fractal, which can be seen in many familiar branching shapes such as fern leaves and even river networks.

Rangeomorphs were unlike any modern organism, which has made it difficult to determine how they fed, grew or reproduced, and therefore difficult to link them to any particular modern group. However, despite the fact that they looked like plants, evidence points to the fact that rangeomorphs were actually some of the earliest animals.

The researchers proposed that rangeomorphs absorbed nutrients through their body surface directly from sea water. If so, here’s a problem:

“The oceans during the Ediacaran period were more like a weak soup — full of nutrients such as organic carbon, whereas today suspended food particles are swiftly harvested by a myriad of animals,” said co-author Professor Simon Conway Morris.

Starting 541 million years ago, the conditions in the oceans changed quickly with the start of the Cambrian Explosion — a period of rapid evolution when most major animal groups first emerge in the fossil record and competition for nutrients increased dramatically.

This analysis has at least the advantage of making more sense than the claim that rangeomorphs were “a ‘failed experiment’ of evolution.” Quite the opposite:

“These creatures were remarkably well-adapted to their environment, as the oceans at the time were high in nutrients and low in competition,” said Dr Hoyal Cuthill. “Mathematically speaking, they filled their space in a nearly perfect way.”

But then the the space changed. Something like that probably happened to the trilobites too.

Reference: Jennifer F. Hoyal Cuthill and Simon Conway Morris. Fractal branching organizations of Ediacaran rangeomorph fronds reveal a lost Proterozoic body plan. PNAS, August 11, 2014 DOI: 10.1073/pnas.1408542111

Abstract The branching morphology of Ediacaran rangeomorph fronds has no exact counterpart in other complex macroorganisms. As such, these fossils pose major questions as to growth patterns, functional morphology, modes of feeding, and adaptive optimality. Here, using parametric Lindenmayer systems, a formal model of rangeomorph morphologies reveals a fractal body plan characterized by self-similar, axial, apical, alternate branching. Consequent morphological reconstruction for 11 taxa demonstrates an adaptive radiation based on 3D space-filling strategies. The fractal body plan of rangeomorphs is shown to maximize surface area, consistent with diffusive nutrient uptake from the water column (osmotrophy). The enigmas of rangeomorph morphology, evolution, and extinction are resolved by the realization that they were adaptively optimized for unique ecological and geochemical conditions in the late Proterozoic. Changes in ocean conditions associated with the Cambrian explosion sealed their fate.

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Why did the Ediacarans go extinct?
Dunno. To get to the other side? -Q (It's getting late) Querius
Plants/vegetation go way way back before the Cambrian. Photosynthesizing Cyanobacteria go back billions of years. They are the oldest fossils. Land was green long long before Sea Life. Genesis for the win:) http://www.ucmp.berkeley.edu/bacteria/cyanofr.html ppolish
Not at Sea, Geologist Proposes - Dec. 12, 2012 Excerpt: Ediacaran fossils, he said, represent "an independent evolutionary radiation of life on land that preceded by at least 20 million years the Cambrian evolutionary explosion of animals in the sea." Increased chemical weathering by large organisms on land may have been needed to fuel the demand of nutrient elements by Cambrian animals. Independent discoveries of Cambrian fossils comparable with Ediacaran ones is evidence, he said, that even in the Cambrian, more than 500 million years ago, life on land may have been larger and more complex than life in the sea. Retallack leaves open the possibility that some Ediacaran fossils found elsewhere in the world may not be land-based in origin, writing in his conclusion that the many different kinds of these fossils need to be tested and re-evaluated. "The key evidence for this new view is that the beds immediately below the cover sandstones in which they are preserved were fossil soils," he said. "In other words the fossils were covered by sand in life position at the top of the soils in which they grew. In addition, frost features and chemical composition of the fossil soils are evidence that they grew in cold dry soils, like lichens in tundra today, rather than in tropical marine lagoons." http://www.sciencedaily.com/releases/2012/12/121212134050.htm Early Life in Death Valley - April 24, 2014 Excerpt: In 2009, Knauth and Martin Kennedy of the University of California, Riverside, shocked their more conservative colleagues with a meta-analysis of thousands of geochemical records from around the planet. They reported additional evidence that a land-based explosion of photosynthesizing algae, mosses, fungi and other organisms was likely to have greened the continents and facilitated the global expansion of multicellular life (including animals) as long ago as 850 million years ago,,, This idea is still quite controversial. Some paleoscientists who agree with Knauth that Precambrian lands were green with microbiota do not believe that early animals, or their precursors, were necessarily lurking in those bacterial jungles. “It is unlikely that animals evolved on land prior to the Cambrian explosion,” Awramik said, noting that Knauth’s theory is not supported by hard fossil evidence. https://www.simonsfoundation.org/quanta/20140424-early-life-in-death-valley/ Many times atheists will attack the Genesis account of creation by saying that plant life on the land did not precede the Cambrian explosion of animal life in the seas as the Bible’s account in Genesis says it does. But the preceding studies indicate that the Genesis account is, once again, proven correct: Genesis 1:11-12 Then God said, “Let the land produce vegetation: seed-bearing plants and trees on the land that bear fruit with seed in it, according to their various kinds.” And it was so. The land produced vegetation: bornagain77
The fractal nature of the those Ediacarans in the OP are simply awesome. Here is Dr Jason Lisle giving a talk on fractals, the "Secret Code of Creation"; http://www.youtube.com/watch?v=nkwCl0ymTfg&feature=youtube_gdata_player I watched this months ago, and if you can bear with the "technical difficulties" I think many will find it interesting. If you like fractals that is:) ppolish
Creations pop into existence and then pop out of existence. Bubbly Tree of Life lol. "But we all descend from the Original Bubble" Um, there was no original bubble that bubbled bubble#2 who bubbled bubble#3... OOL was bubbles all over the Earth at about the same time. Some Creation Bubbles last millions of years before popping. The Ediacarans popped long ago. ppolish
Where have all the Edicarians gone? Long time passing.. Gone for Cambrians, every one. OldArmy94
OT: In salute to Robin Williams What Dreams May Come Ending Theme - music https://www.youtube.com/watch?v=w7ZOjHEqW7M bornagain77

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