570 million year old animal life form

  • #1
Tom.G
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Seems that us animals got an even earlier start than we thought.

Short popular version:
https://www.livescience.com/63289-ediacaran-leaf-fossil-is-animal.html

Longer version:
http://www.dailymail.co.uk/sciencet...DER-previously-thought-scientists-reveal.html
(different subject, but article is followed by a short interesting video)

Full Scientific article:
https://onlinelibrary.wiley.com/doi/full/10.1111/pala.12393
https://doi.org/10.1111/pala.12393
 
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Answers and Replies

  • #2
BillTre
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The frond-like fossils of the Ediacaran have been known for a long time.
This article describes some frond animals in the Cambrian period which followed the Ediacaran.
Some of the Ediacaran frond animals resided in deep water, indicating they were not plants (no light).
Not sure how they ruled out them being fungi.

They got a lot of samples and did an analysis of their fossil's morphology which indicates they arose between sponges (filter feeding, sedentary, animals with no nervous system, muscles or digestive system) and later arising animals with digestive systems (almost all other animals).
Some think the frond animals were not filter feeders (unlike sponges), but instead absorbed nutrients from the water.

They can get somewhat big (10's of cms to a meter), but they have a fractal-like branching structure.
To me, this indicates they used a same or similar developmental program to generate their structure at different scales, or that they grow somewhat like a tree (grow, branch, grow larger while doing more similar branching on a smaller scale).

Besides fossils, molecular data are used to determine when different taxa arose.
Fossils of early animals are limited by the difficulty of the famous Cambrian Explosion was not the beginning of animal life, but a great expansion of the different forms of animals and a great increase of relatively easily fossilizable dead animals due to their evolving of hard body parts that would not easily rot away when dead.
Extraordinary fossil assemblages of soft body fossils are unlikely occurrences where a large amount of mud slumps off an underwater cliff an buries an area containing a lot of soft body animals while excluding oxygen. There may also have been other special chemical conditions that promoted their fossilization.

Molecular studies indicate that animals originated prior to the Ediacaran. Molecular estimates of species divergence times (when a group might have originated) can be calibrated by comparing with the first appearance of fossils for a species, if they exist. However fossils of the first animals (assumed to be small, one or a few mm) are very rare to find so this approach can not be used.
 

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