Devonian Spiny Nautiloid

Discussion in 'Cephalopod Fossils' started by Hajar, Oct 14, 2010.

  1. Hajar

    Hajar Haliphron Atlanticus Registered

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    Here's an interesting thing; a 7 cm Early Devonian nautiloid from Eifel, Germany with a number of partially preserved large tubercles. It looks quite similar to Hercoceras though the height/width ratio of the whorls seems higher than in that genus. I like the painting by Jan Sovák.

    Does anyone have similar spiny nautiloids or have more of an idea about the identification?
     

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  2. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    Looking at the "bumps" gave immediate thought about how similar they look to the papilliae that many octopuses and cuttlefish can produce on their skin.
     
  3. Hajar

    Hajar Haliphron Atlanticus Registered

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    Reading the paper a bit more carefully I see that Turek describes Hercoceras mirum as a "highly variable species" and he writes that "the shape of the cross-section varies greatly".
     
  4. Hajar

    Hajar Haliphron Atlanticus Registered

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    I see what you mean D (having just looked at a photo of an Enteroctopus dofleini). Most of the bumps on the fossil are just the bases of initially longer spines (as shown in the painting).

    On mode of life, Turek writes "the poor hydrodynamic properties of the shell of H. mirum is interpreted here to indicate a benthic habit with a limited ability for active swimming."
     
  5. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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  6. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    Cooperoceras from the Late Paleozoic is similar.

    It looks like your on the right track for an ID.

    These nodes and/or spines, like a lot of those on ammonoids, have the look of a support for a couple of specialized arms, kind of like a groove for the arm to fit in, or maybe papillae guides. ?? :hmm:
     
  7. Hajar

    Hajar Haliphron Atlanticus Registered

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    I was completely amazed when first I saw cuttlefish doing that: one second smooth and pale blue-grey; the next patterned browns with long tubercles. I wonder what use these nautiloids had from their spines (and "wings" in the case of Ptenoceras). Enhanced stability?
     
  8. Hajar

    Hajar Haliphron Atlanticus Registered

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    Thanks for that excellent link Kevin. I had not seen that!
     
  9. Hajar

    Hajar Haliphron Atlanticus Registered

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    I just noticed that Cooperoceras is from the Glass Mountains so there are probably some spectacular etched out silicifed specimens. have you ever seen one?
     
  10. Hajar

    Hajar Haliphron Atlanticus Registered

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    Here it states that after 12 years of intensive collecting they found just two fragments, the holotype and a paratype.
     
  11. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    A couple of pics (pirated :goofysca:) of nautiloids from the Treatise.

    Is your specimen Torticonic?
     

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  12. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    Kevin,
    Were the horns in the shells hollow?
     
  13. Hajar

    Hajar Haliphron Atlanticus Registered

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    Excellent Cooperoceras image Kevin. Thanks. That Hercoceras seems to have lost its spines, probably an internal mould.

    My specimen could be gently torticonic, but it's a bit difficult to see. The shell has gone from the other side (so there's a smooth internal mould without tubercles) and the centre is not yet exposed. The observation that the tubercles don't show on the internal mould suggests that the spines were not hollow. On a quick search though it seems that Cooperoceras spines were hollow; Flower (1949) talks about solid nodes; Turek writes "Parabolic ventrolateral outgrowths, which appeared earlier in the ontogeny, show a tendency to transform into hollow adaperturally opened spines." Don't know, but with the single specimen I have in hand I'd say "not hollow".
     
  14. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    Thanks Hajar,
    I would never have thought about the possibility except for one looks hollow in Kevin's pirated picture and it was even more interesting to think that cephs could for internal papillae while they had shells. Obviously this would not have been for camouflage but could be another case where, like poison, a biologic feature evolved a new use. Kind of exciting to my little brain :grin:
     
  15. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    I think that while the spines were forming they were crescent shaped half spines, the mantle (or arm? or papillae?) extended to the end of the spine. As the shell grew it eventually closed off forming a hollow spine. Most were probably sealed off with a plug (see post 66 in this thread), the position of the plug in the spine determined the size of the node on the internal mold. In the attached photo, this critter formed a single pair of spines, probably after reaching maturity, the internal mold here would be as long as the spine. Parabolic nodes such as in Hercoceras were probably kept in the crescent form until the next spine was ready to form, whereas in Cooperoceras, the shell grew continuously (not seeing the internal mold in the pic, I can't see if it had a plug or not). Of course there are probably as many ways to form a spine as there are different forms of shells so the growth lines on different forms would have to be followed to see how each was made. :talker:
     

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  16. Hajar

    Hajar Haliphron Atlanticus Registered

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    Brilliant Link Kevin - the same discussion but for ammonites. Solenochilus is another beast I had never heard of before. It's quite dramatic. Have you read any discussion of the possible purpose/use of this single pair of long hollow spines?
     
  17. Hajar

    Hajar Haliphron Atlanticus Registered

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    Here's a photo to show a horn (length about 8 mm) on the shell of the nautiloid and the smooth internal mould on the opposite side.

    I also just took a photo of two of the horns of a weathered Omani Cunningtoniceras showing that these horns had no internal plugs. Field of view about 7 cm wide.
     

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  18. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    No, I have not read a discussion on these. Just as conjecture though, extant Nautilus has a pair of arms(?) just behind the eye that would assume the same position as these spines, could the spines be an extension and/or support for whatever purpose these "occular arms" have? And could similar spines on other shelled cephalopods have the same purpose, only form iteratively?


    That smooth opposite side could be the sign of a torticonic shell, or that the spines were solid and independent of the body chamber, or possibly even some kind of pathology. Is there any sign of spines at all on the opposite side?

    It looks like the horns on Cunningtoniceras were just enlarged nodes, with just the shell covering them, no elongated spines to speak of. :smile:
     
  19. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    Now I am wondering why they would grow a hollow spine and then a plug. All these animals were permenantly attached to their shells, right?
     
  20. Hajar

    Hajar Haliphron Atlanticus Registered

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    Here's another picture of the nautiloid Kevin showing the broken edge of the shell, which is about 1 mm thick, and the smooth internal mould on the other side from all the horns. No bumps on that side as far as I can see so I'd guess that the spines/horns were solid.

    I like the arm support idea. I just read that the "name "Nautilus" originally referred to the Argonauta, otherwise known as paper nautiluses, because the ancients believed these animals used their two expanded arms as sails."

    In your ammonite spine/plug link above Kevin the photo shows multiple laminae (at least 4 including the "plug") in the shell. ?successive episodes of secretion from within, each addition filling more of the spine?
     

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