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Yesterday I hunted an Upper Santonian Austin Chalk site in Ellis county between downpours of rain. This was my first time at the site. I was looking around a pile of rocks with some boulders mixed in and found this on one of the boulders. It is tiny, whatever it is, about 1 cm wide. Now I must admit that I am more familiar with the fauna of the Upper Coniacian Austin Chalk but to me this looks more like half of the aptychus of an ammonite than a bivalve. Since an aptychus was made of calcite I believe that it would be preserved in chalk, though the actual fossilized material is gone and this is just the steinkern of what ever it was. Here is the best picture that I have of it. Sorry that the quality is poor. I took it while I was at the site and I can’t get a better picture right now. Hopfully this will be sufficient.
bugsheep posted a topic in Questions & AnswersI have a few questions I’m unable to answer about ammonites. I’ve been doing some casual research, but it seems to lead to more confusion on this. I would really appreciate it if anyone could suggest more sites to look at as well. What kind of shell “decoration” is present on ammonites with ammonitic sutures? Was there any “normal” combination of shell and suture mark, or could their shells have any pattern of ridges, knobs, etc.? I’ve been hoping to find a sort of before and after polishing photo/sketch set, showing what shell went with what suture pattern, but have been unable to find anything. While trying to find the photo/sketch, I realized all photos of ammonitic sutures I’d found were of creatures that were involute, the outer whorls almost completely covering the inner. Is this just a coincidence, or were most/all ammonites with ammonitic sutures so involute? Also, did any/some/many/all ammonites with ammonitic sutures have an aptychus? I've been able to find all sorts of information on these features individually, but not on co-incidence, so to speak.