Ammonid longevity

Discussion in 'Cephalopod Fossils' started by DWhatley, Apr 24, 2012.

  1. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    First fertile, then futile: ammonites or the boon and bane of many offspringUniversity of Zurich, April 23, 2012

    This sounds very similar to what Dr. Gilly recently observed with the size and reproduction age of the Humboldt squid.

     
  2. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    Phylogeny vs Ontogeny :heee:

    Is there a link or something to Dr. Gilly's observations?
     
  3. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    Shoot Kevin, I knew someone would ask, let me try to find it.

    OK, this one should do but Googling Gilly squid small brings up several more articles.
     
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  4. hallucigenia

    hallucigenia O. bimaculoides Supporter

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    Hmm. That's interesting because stuff looking at end-Cretaceous extinction selectivity and larval type has found none, either in gastropods (Jablonski 1986 and many times thereafter) nor in sea urchins (Smith 1998). Of course it's possible they screwed up their methods somehow; diversity analysis is Hard and I have heard some concerns regarding at least Jablonski's methodology in that study.

    However, taking the existing research at face value, what might be the factor that made the extinction selective for ammonoid larvae but nobody else's? Landman, btw, is pretty convinced that most ammonoids were not predators in the classical sense, but probably mainly filter-feeding -- if you remember that one paper about the soft parts, that's the explanation.
     
  5. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    Perhaps water depth (?floating ammonoid egg masses/larvae? benthic others?). Ammonoids did survive the PT event, the most severe, what was different with the KT event?
     
  6. Pr0teusUnbound

    Pr0teusUnbound GPO Registered

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    one thing ive noticed when reading up on ammonoids is that two of their major adaptive radiations coincided with similar radiations in fishes. when ammonoids first appeared in the Devonian, fishes like placoderms and chondrichthyans were already all over the place. in the Cretaceous, heteromorphs started popping up right after teleosts experienced their own radiation. perhaps their evolution was driven interactions with jawed fishes. and more to the point, perhaps these new teleost predators may have been too much for them to handle, which could be one of the reasons why they failed to survive the K-T extinction (despite surviving some many previous events).
     
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