references for ammonite species ID by suture lines?

Discussion in 'Cephalopod Fossils' started by monty, Apr 8, 2007.

  1. monty

    monty Colossal Squid Staff Member Supporter

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    Hi, all.

    When I was at the Hilo Farmers Market the a few weeks ago, the local hippie-crystal-cool-rock dealer had a number of ammonites for sale, and I bought 3 specimens I thought were nifty (although I couldn't really ID them particularly at all.) I chose 3 that had some view of the suture lines, although no complete suture all the way around.

    Between Kevin's and Phil's articles and the Monks and Palmer Ammonites book, I know that there's a wide variety of complex suture lines in different species, and that there's a standard way to draw the suture line "unwrapped," but I'm wondering if there's an online reference that allows one to compare a suture line to species to find a match somehow? It looks like wikipedia is starting a big list-o-ammonites here: http://en.wikipedia.org/wiki/List_of_ammonites but it doesn't include suture lines and it's pretty spares except in the A's.

    I assume that these are likely to be common and boring specimens, and I'm not sure if they were polished in a way that all you fossilhounds would scoff at, but I figured it'd be a good learning experience to try and ID them... she thought they were all from Madagascar, but wasn't positive... she tended to get Madagascar, Indonesia, and Malaysia mixed up...

    I'm also curious if I got a good deal, or if these are a dime a dozen... I think I paid $80 for 3 prepared specimens: $15 for a small one that's the least prepared, $30 for a similar one that's cut into two halves down the center, and $35 for a big polished one that's got most of the shell polished away, but has much more visible suture lines. They might all be the same species, at least they're all planispiral, involute, oxycone, although the one that's cut in half seems to have less ribbing. They all have typical-looking complex septa showing in at least a small area. Ribbing is simple and slightly curved on the 2 that have a lot, like pictures of scaphites I've seen, and any lappets are long gone. There's some iridescence in the remaining shell parts.

    (where do you measure diameter, anyway? the big one is 8cm perpendicular to the aperture, 10cm including the aperture. The others are around 2cm and 3cm)

    more pics here.
     

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  2. sorseress

    sorseress Colossal Squid Supporter

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    I have a few, my biggest is 5" by 6". My others range from 1 1/2" by 2" to 3 1/2" by 4". They are all polished on the cut face, some polished on the outer surface, some not. The big one was $12.00, the smaller ones were $6.00 each. I wish I knew what happened to all the ones we dug out of our backyard in Texas. some of them were a foot across. Erich??? :earlyammo
     
  3. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    Some very pretty ammonites Monty, they do look like the ones from Madagascar.
    As for suture comparison, it is in its infancy but they are starting to use GIS (Geographic Information System) software to compare sutures. Here is one example.
     
  4. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    Measure the diameter across the widest part, from the end of the aperture on the ventral side, thru the umbilicus, to the opposite ventral side. The 10cm measurement would be the one to use.
     

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