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THE CAMBRIAN "EXPLOSION" WASNT SO EXPLOSIVE

 
 
Reply Tue 7 Aug, 2012 06:01 am
Findings from fossils of the Ediacaran times (late pre Cambrian) now show that several metazoan species actually had exoskeletal structures. Up until recently,The CAmbrian Explosion has been defined as a 20 million year period within which fossil species had suddenly developed and carried exoskeletons, shells and, in some cases, remnants of notochords.
The Itapucumi Group of Formations in PAraguay is of the Ecdiacaran times and these formations show that several species of Ediacaran metazoan fossils actually secreted biomineralized skeletal structures and shells much earlier. These fossils clearly start the "Explosion" that resulted in complex body structures and larger frames many tens of million years earlier than originally assigned.
The Itapucumi Group represents a sequence in time that extends the Cambrian Explosion backward another 30 million years at least. This means that the formation of skeletal structures had begun at least 580 myA . So we have a Cambrian Exlosion that is about 50 million years in length , roughly the equivalent of the time from the Eocene to today.

(Source: GEOLOGY v 40, no 8 .p 691)

 
jespah
 
  1  
Reply Tue 7 Aug, 2012 06:55 am
@farmerman,
Well, I imagine fossil collection, analysis and detection are getting better all the time. Kinda makes sense that it wouldn't all just spring up quickly (relatively speaking). How 'bout them trilobites?
raprap
 
  4  
Reply Tue 7 Aug, 2012 07:00 am
@farmerman,
Hard to consider something that occurred over a period of 50 million years and explosion. But the Cambrian was also geologically active period with the creation of the Appalachians and continants splitting and recombining. Lots os new stresses and new niches. Arthopods ruling the fauna and flora creating an oxidizing environs to replace the reducing one.

I has a High School Freshman Physical Science Class prepare a scaled timeline in the hall of the school hall in the plains of Colorado--starting with the formation of the earth and ending with Rome. It was up during the fall semester parents teachers conferences and I recieve a few complaints from parents, because it offended their biblical sensibilities. In the spring I had this class construct a scale model of the solar system in outside along the side of the football and baseball fields. Again I recieved complaints from the same parents for the same reasons.

My contract wasn't renewed the next year--I put it down to the following factors. I wasn't a local, I offended sensibilities by illustrations of how insignificant the human species and this little rock really was (especially as Proxima Centauri, the nest nearest star, was in Wray, w25 miles away), I rode a bicycle on Sunday morning, science was in conflict with biblical innerrancy, and the student body was rapidly becoming a hispanic majority as the local arga-business became corporate.

I learned something from that experience--corporations don't really want an educated and curious workforce--they prefer a trainable one, there's a significant hostility when you expose a dissonance between facts and long term fictions, I didn't like teaching adolescent teens in classrooms, I am not suited to life in the arid plains. I guess its all well that I abandonded that life.

Rap
farmerman
 
  1  
Reply Tue 7 Aug, 2012 07:20 am
@jespah,
These are all relatively new fossil finds and analyses. Just as several fossil assemblages had been located using a "falsification premise" so has this fossil assemblage been discovered based upon a reassembling of the old cratonic shelf land of "Ur". Ur was part of a pre Cambrian "Supercontinent" called Columbia. The Ur segment was an inner cratonic shallow sea that stretched from the Paraguay Brazil area of S America, through Central Africa and on to the adjoined and conjoined landmasses that would become India and Australia.

SO, weve known a long time about the Ediacaran assemblages from the place of the same name in AUstralia BUT, few have taken the "falsification step" to prove or disprove the reassembled forelands of UR and its contained fossils.
UR had a lengthy history of stratigraphy through the time of the end of the great "Iceball Earth " period called theCryogenian period, and until the first breakup of Columbia into the preOrdovician landmasses ( roughly 600 myA till about 440myA)
So, several expeditions were mounted in the early 200's to inspect these possible Ediacaran areas in places like Africa nd South America. Many of these assemblages were, as wed expect, fully distorted an remelted due to later continental collisions and metamorphism. However, there were several sites, including the Itupucumi group located west of the Paran'a Basin. Several distinct fosils of the Ediacaran were found. DAting showed these to be slightly younger than the type section fossils in Australia so the evidence of these animals evolved exoskeletons was a possible consequence of the changing chemistry of the water (ion assemblages show that the water became enriched in Ca/Mg ) Alo, the study report speculated that extreme predation by larger and larger forms of several metazoans was apparently instrumental in several of these animals were developing exoskeletons as protection against predation.

jespah
 
  1  
Reply Tue 7 Aug, 2012 07:24 am
@farmerman,
It continues to amaze me how the envelope keeps getting pushed on this.
farmerman
 
  2  
Reply Tue 7 Aug, 2012 07:30 am
@raprap,
Quote:


Hard to consider something that occurred over a period of 50 million years and explosion


Thats pretty much the whole point. All the research that went into this paper was done by the Universtdade de Sao Paulo, in Brazil and the Industria Nacional de CEmento, Vallemi Paraguay. Id imagine that unlimited funding to go on a search that is based upon a Popperian premise would be damn difficult in US. Its getting harder and harder to extract funding for straight exploration research unless theres a product in the pipeline.

Worldview still hold us back in many disciplines, evolution being a huge one. Most evo/devo work is being conducted by medical schools today in US. Exploration studies (like the hunt for Tiiktalik) just arent very popular, even with heavily endowed museums.


farmerman
 
  1  
Reply Tue 7 Aug, 2012 07:34 am
@jespah,
We learn some ****, and then, jut as we all get comfortable with it,(and the Creationists start preaching how a benevolend God thought it all up) someone comes up with some new **** that demolishes the old ****. I sorta like my science that way,it keeps ya on your toes and keeps your mind young.
0 Replies
 
jespah
 
  2  
Reply Tue 7 Aug, 2012 08:46 am
@jespah,
Cripes, double post. Well, I'm doubly fascinated.
farmerman
 
  1  
Reply Tue 7 Aug, 2012 09:38 am
@jespah,
we need to rename the cambrian explosion to something more appropriate.
rosborne979
 
  1  
Reply Tue 7 Aug, 2012 10:07 am
@farmerman,
farmerman wrote:

we need to rename the cambrian explosion to something more appropriate.
The Cambrian Crawl?
raprap
 
  1  
Reply Tue 7 Aug, 2012 10:31 am
@rosborne979,
It was faster than a 'crawl'--perhaps a 'trot'.

Rap
farmerman
 
  1  
Reply Tue 7 Aug, 2012 12:41 pm
@raprap,
The Cambrian Trot(s). Sorta makes it sound urgent but not sxplosive
jespah
 
  1  
Reply Tue 7 Aug, 2012 03:57 pm
@farmerman,
Have you never had the trots? They can be really explosive.

The Cambrian Cha-Cha
farmerman
 
  1  
Reply Wed 8 Aug, 2012 04:39 pm
@jespah,
Some of the more advanced Ediacaran fauna
    http://t1.gstatic.com/images?q=tbn:ANd9GcRWpWvhGG3B_khjW8cRFCRD12zD1_ZlZLdIWzqPaQhj0-2Lh8O3                                MICRODICTYON

     http://upload.wikimedia.org/wikipedia/commons/1/15/Waptia.png

WAPTIA
jespah
 
  1  
Reply Wed 8 Aug, 2012 04:48 pm
@farmerman,
Eek, I am gonna have dreams about them now.
farmerman
 
  2  
Reply Wed 8 Aug, 2012 06:30 pm
@jespah,
you can see the carapace on the Waptia fossil and the jointed legs on both. HArdly a" protoplasmic mass". All of these specimens are from genera that have no descendants. The MICRODICTYON had a decsendant form that was seen in the Burgess shales of mid Cambrian, then they too vanished.
edgarblythe
 
  1  
Reply Wed 8 Aug, 2012 06:38 pm
@farmerman,
Likely left off of the ark and they drowned.
0 Replies
 
ossobuco
 
  1  
Reply Wed 8 Aug, 2012 06:42 pm
@farmerman,
Scary, but it makes a sad sort of sense.
farmerman
 
  1  
Reply Wed 8 Aug, 2012 06:54 pm
@ossobuco,
Quote:
Scary, but it makes a sad sort of sense
are you afraid of a little fossil?
ossobuco
 
  1  
Reply Thu 9 Aug, 2012 08:55 am
@farmerman,
That was a reply to this by you -


Worldview still hold us back in many disciplines, evolution being a huge one. Most evo/devo work is being conducted by medical schools today in US. Exploration studies (like the hunt for Tiiktalik) just arent very popular, even with heavily endowed museums.
 

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