Why all the Ammonoid Fossils

DWhatley

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Between new PHd's, new published papers, new up-coming books and new speaking engagements, TONMO is certainly well endowed:glass:
 

Phil

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Good luck Kevin. You'll be just great. I hope you enjoy the experience as much as the audience enjoys listening to you!

Pity we can't pod-cast your lecture here. Or can we, Tony?
 

Architeuthoceras

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Thanks for the encouragement Phil, but as the time gets closer the knee shakes get stronger and the lips quiver faster. I thought about picturing the audience naked, but realized they would probably be alot of old bearded paleontologists and the shakes got worse. :goofysca:
 

Architeuthoceras

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It turns out there are alot more young ladies becoming paleontologists these days, and picturing them naked just made me forget half the talk. It got said at any rate.

Basically the answer is #2- Toxic environment, anoxia to be specific, or #5- a combination. A global warming event, caused by increased atmospheric CO2 (probably from volcanism in Siberia), changed the latitudinal temperature gradient of the Panthalassic ocean causing an ammonoid extinction between the beds with Inyoites and the beds with Anasibirites. Faunas before this event were high diversity and latitudinally restricted, those after were low diversity, cosmopolitan faunas. The Prionitids (the family containing Wasatchites and Anasibirites) somehow survived this extinction and proliferated. So it may be that there was just alot of ammonoids or an "Anasibirites bloom". An anoxic event that started in the beds below the Inyoites beds and reached its peak sometime during the time the Anasibirites beds were being deposited (before, during or after the beds in our study?) probably was the final straw for the Prionitids as they too went through an extinction at the end of the Smithian Stage. Ammonoids in the following Spathian Stage started to regain their high diversity, latitudinal restricted, normal existence. So, really, all this just brings up more questions. :wink:

a few references:
Galfetti et. al. 2007a
Galfetti et. al. 2007b
Brayard et. al. 2006
 

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