10 million or 1 million

Discussion in 'Cephalopod Fossils' started by Architeuthoceras, Jan 18, 2011.

  1. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    This study says 10 million years to recover from the PT event.

    This study says 1 million years to recover from the PT event.

    I assume both studies used databases of ammonoids, and probably previously published. Am I not reading them right, or are they reading the data differently?

    :shock:
     
  2. POD-L

    POD-L O. bimaculoides Registered

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    Kevin
    I think a lot of math is involved to "normalize" the data , depends on what equation and data manipulation is used. I remember a similar debate over how soon ammonites disappeared at the KT boundary. Some consider them to be on their way out millions of years before KT. Peter Ward did a study at the KT boundary in Spain and discovered they were well represented right up to the boundary. Analysis is a lot like statistics!
     
  3. hallucigenia

    hallucigenia O. bimaculoides Supporter

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    I blame this. :nyah:

    First appearances and last appearances are hard, and it's all about what method you use to estimate them.
     
  4. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    If the fossil record was perfect I suppose the two numbers would be a little closer. The dating of the rocks may also play a role in the two results. The number of different phyla used to calculate diversity may skew the results. But they both used ammonoids. :hmm:
     
  5. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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  6. Hajar

    Hajar Haliphron Atlanticus Registered

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    Have you read the two papers Kevin? Do they have the same definition of recovery?

    Brayard et al. looks like a thorough piece of work. They say "This explosive and nondelayed diversification contrasts with the slow and delayed character of the Triassic biotic recovery as currently illustrated for other, mainly benthic groups such as bivalves and gastropods."
     
  7. Hajar

    Hajar Haliphron Atlanticus Registered

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    By the way, I liked the discussion and reply on your "Gastropod evidence against the Early Triassic Lilliput effect" paper.
     
  8. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    The library here doesn't have a subscription for electronic copies, the hard copy comes about the middle of the month, so I am patiently waiting. :sad:

    From the news release I assume Whiteside & Ward are using morphotypes to determine swimmers and floaters, with the return of the swimmers bringing recovery. Brayard et al, counted genera, comparing the numbers with Permian and later Triassic numbers. Of course they both use the Carbon isotope cycles to help calibrate time.

    Just as a side note, in my experience, the Smithian rocks (~1.5-2 My post P/T) in Utah have more diversity in both genera and morphotypes than any other bed of any age I have collected.

    Thanks! A lot more defence needed in science than I had imagined. :sly:
     
  9. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    I just got a copy of the Whiteside & Ward paper... verrrry interesting :grin:

    They attribute the "chaotic" Carbon Isotope Cycles to a destabilized ecosystem (functional redundancy) rather than volcanogenic CO2. They discount eustasy on statistical grounds.



    On the time scale above, their "Chaotic carbon" episodes correlate (P/T & T/J boundaries) with some "Chaotic sequences" (eustacy), that may or may not correspond with the carbon cycles, and that could be of volcanic and/or glacial origin, rather than biologic.
    There is probably a middle ground somewhere, when all things are considered (more study needed).

    Ammonoid wise; they counted genera from the Pacific Coast (paleo?) of North America and divided them into morphotypes. Serpenticones and heteromorphs are considered floaters and all others swimmers.
     

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