Belemnite Extinction

Discussion in 'Cephalopod Fossils' started by Phil, Jun 29, 2003.

  1. Phil

    Phil Colossal Squid Supporter Registered

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    Many months ago this topic was brought up but we did not really come to a conclusion. As almost a thousand people have joined this website since the question was originally posed, it is worth repeating to determine if anyone has any fresh perspectives or information on the matter.

    In short, I was always under the impession that belemnites became extinct along with ammonites at the end of the Cretaceous period. Yet I noticed in EH Clarkson's Invertebrate Palaeontology and Evolution 4th ed. (1998), mention was made of a few belemnites continuing into the Tertiary before becoming extinct. This is very interesting but unfortunately the book did not quote the reference for the claim or the location of these anomalies. Personally I would assume that these rare finds may be redepositions from earlier contexts, but this is merely a gut reaction.

    Does anyone have any further information on these enigmatic survivors or is it all a question of misinterpretation of contexts?
     
  2. Neale Monks

    Neale Monks Cuttlefish Registered

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    re: Belemnite extinction

    Phil,

    Last time I checked, the supposed Tertiary belemnites ("Bayanoteuthis") were now interpreted as some other fossil type, perhaps even the stem of a sea pen (pennatulacean octocoral). I think the first ones were found in Israel but I'm not sure. See Doyle in "The Fossil Record 2", 1994. I've looked at them, and I'll admit they're very like a belemnite, but then so is any other long thin piece of calcite...

    Anyway, these are things Clarkson will be referring to. His text book is good as far as it goes, but the ceph section is not all that strong and in many ways very dated. Other than this fossil, the belemnites definitely went extinct at the end of the Cretaceous, and are pretty scarce by the Maastrichtian. There's a _very_ useful PDF here on K/T extinctions:

    http://pcwww.liv.ac.uk/~chj/jgeolsoc.pdf

    There are lots of belemnite-like cephalopods from the Tertiary, the Spirulirostridae most notably. These have the coiled Spirula shell but with an odd calcitic "guard" sticking out the back with the shell itself sitting underneath in a sort of sheath. A most peculiar arrangement, I wrote a short paper on these things, and postulated that as juveniles they must have lacked the guard and hung head downwards, and then developed the guard only as maturity approached and the shell reached full size. With the guard present they were counterbalanced with the head horizontal. The upshot of all this was the hypothesis that Spirula was a paedomorphic Spirulirostra, retaining the juvenile head downwards morphology into maturity.

    Some extant squids have a strikingly belemnite morphology, Moroteuthis springs to mind here. It has a whopping great guard at the end of the pen, admittedly not calcite, but still circular in section rather than flattened.

    Cheers,

    Neale
     
  3. Phil

    Phil Colossal Squid Supporter Registered

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    Neale,

    Thank you very much for taking the time to explain the details surrounding these supposed belemnite survivors; that certainly clears that one up for me. I’ve had a look at the article you linked to, it mentions Bayanoteuthis and states that it at least one researcher (Doyle) has excluded it from the belemnitida anyway. It is interesting that it may have misinterpreted as a sea pen, it would be nice to have a look at an image..

    By the way, ‘Palaeobase 2’ plopped onto my doormat this morning, and I’ve been having a look around it this afternoon (sometimes getting lost!). That really is an amazing collection of detail and images. How on earth do you choose the specimens? I realise that some are obvious choices but there must be so many interesting specimens that must get left out. I particularly liked the image of the Cretaceous Palaeoctopus newboldi, that was indeed a beautiful specimen. It is amazing how much this animal resembles modern deep-water cirrate octopuses, with those small triangular fins on its body. It certainly seems to be reminiscent of Grimpoteuthis or maybe Opisthoteuthis, especially if there was indeed a web that extended between the arms as is suggested.

    I had a look at Spirulirostra too; it’s great to see images of the specimen you describe. As for Moroteuthis, there are some superb images on this thread that I think you might enjoy of a recently washed up, and still alive, specimen:

    Squid (unquestionably) washes up in Puget Sound

    Thanks again!

    Phil
     
  4. Neale Monks

    Neale Monks Cuttlefish Registered

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    Phil,

    Below is a picture of Bayanoteuthis, from the Natural History Museum collections in London. Please don't anyone reproduce this image without permission.

    Cheers,

    Neale
     
  5. Phil

    Phil Colossal Squid Supporter Registered

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    On the topic of belemnites, here is a quite interesting photo of a Jurassic belemnite battlefield. Some of these animals must have swum in densely packed shoals. Perhaps we are looking at a mass mortality here, following spawning, perhaps? The direction of the belemnite rostra demonstrates the direction of the current at that time.

    [​IMG]

    Public access image. Copyright © Martin Miller, University of Oregon. Image Copyright © United States Geological Survey; Image courtesy Earth Science World ImageBank http://www.earthscienceworld.org/imagebank
     
  6. Phil

    Phil Colossal Squid Supporter Registered

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    Well, perhaps not spawning. There seem to be different sizes of rostra in there, which would seemingly indicate animals of different stages of maturity.

    Thinking out loud here.
     

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