Micah Posted February 10, 2020 Share Posted February 10, 2020 My dad happened to be in Tucson during the fossil show and grabbed a neat sliced ammonite in a box simply labeled “made in Madagascar” (he knows I’m a sucker for any fossil that had a geode develop in a cavity). I’d like to know a bit more about it, but the info I’ve been able to find about the ammonites of Madagascar is pretty limited and makes identifying pretty hard. My best guess is Desmoceras sp. can anyone be more specific or correct me? Link to comment Share on other sites More sharing options...
Bobby Rico Posted February 10, 2020 Share Posted February 10, 2020 It is difficult with the outside missing a lot of it’s form . You could look at Cleoniceras as a start. Nice looking ammo. Link to comment Share on other sites More sharing options...
Micah Posted February 10, 2020 Author Share Posted February 10, 2020 50 minutes ago, Bobby Rico said: It is difficult with the outside missing a lot of it’s form . You could look at Cleoniceras as a start. Nice looking ammo. Thanks :-) I’m enjoying it! At least where I was looking Cleoniceras has (For lack of a better word) squiggly walls between its cameras while Desmoceras has smooth curves... idk if that’s even a distinguishing feature, but the online pictures seem to portray it that way. Link to comment Share on other sites More sharing options...
KingSepron Posted February 10, 2020 Share Posted February 10, 2020 That fire-like pattern is more Cleoniceras to me 1 Link to comment Share on other sites More sharing options...
minnbuckeye Posted February 10, 2020 Share Posted February 10, 2020 3 hours ago, Micah said: I’m a sucker for any fossil that had a geode develop in a cavity) I am just as big of a sucker! Beautiful ammonite!!! Are they calcite crystals? Mike Link to comment Share on other sites More sharing options...
Micah Posted February 10, 2020 Author Share Posted February 10, 2020 5 hours ago, KingSepron said: That fire-like pattern is more Cleoniceras to me I see what you mean now, thanks! I didn’t Realize how important that pattern is to identifying ammonites! Link to comment Share on other sites More sharing options...
Micah Posted February 10, 2020 Author Share Posted February 10, 2020 5 hours ago, minnbuckeye said: I am just as big of a sucker! Beautiful ammonite!!! Are they calcite crystals? Thanks Mike! From what I can tell they are probably white calcite crystals. 1 Link to comment Share on other sites More sharing options...
Ludwigia Posted February 10, 2020 Share Posted February 10, 2020 I think you might be correct with Desmoceras. The whorl cross-section is wider than that of Cleoniceras. Also the shape of the septal walls and the sutures fit better than Cleoniceras in my opinion. 3 Greetings from the Lake of Constance. Roger http://www.steinkern.de/ Link to comment Share on other sites More sharing options...
KingSepron Posted February 11, 2020 Share Posted February 11, 2020 It’d really help to see the middle if you could OP, desmoceras tend to have a deeper inner whorl and be more involute, which we can’t see at the moment 1 Link to comment Share on other sites More sharing options...
Micah Posted February 11, 2020 Author Share Posted February 11, 2020 9 minutes ago, KingSepron said: It’d really help to see the middle if you could OP, desmoceras tend to have a deeper inner whorl and be more involute, which we can’t see at the moment What does op stand for? I’m assuming something to do with removing the matrix. I’ll be honest I don’t have the tools. Link to comment Share on other sites More sharing options...
KingSepron Posted February 11, 2020 Share Posted February 11, 2020 Just now, Micah said: What does op stand for? I’m assuming something to do with removing the matrix. I’ll be honest I don’t have the tools. OP stands for Original Poster 1 Link to comment Share on other sites More sharing options...
Micah Posted February 11, 2020 Author Share Posted February 11, 2020 @KingSepron gottcha. Yea still unfortunately don’t have the tools to expose the whorl on the outside and it’s not really defined on the cross section. Link to comment Share on other sites More sharing options...
KingSepron Posted February 11, 2020 Share Posted February 11, 2020 1 minute ago, Micah said: @KingSepron gottcha. Yea still unfortunately don’t have the tools to expose the whorl on the outside and it’s not really defined on the cross section. Fair enough! How big is it? Link to comment Share on other sites More sharing options...
Mark Kmiecik Posted February 11, 2020 Share Posted February 11, 2020 In the first photo, on the half on the right side, why do the chambers seem to be pointed in the wrong direction and opposite to the other half? Shouldn't the two halves be a mirror image of each other? The longer I stare at them, the less I can wrap my brain around the internal structure. If nothing else, are these halves of two different ammonites? 2 Mark. Fossil hunting is easy -- they don't run away when you shoot at them! Link to comment Share on other sites More sharing options...
Micah Posted February 12, 2020 Author Share Posted February 12, 2020 Woaaaah!!!!! How did I miss that! How on earth did they find two that looked so similar! And fit so perfectly together.... honestly I’m impressed. Link to comment Share on other sites More sharing options...
DPS Ammonite Posted February 12, 2020 Share Posted February 12, 2020 6 hours ago, Mark Kmiecik said: In the first photo, on the half on the right side, why do the chambers seem to be pointed in the wrong direction and opposite to the other half? Shouldn't the two halves be a mirror image of each other? The longer I stare at them, the less I can wrap my brain around the internal structure. If nothing else, are these halves of two different ammonites? Wow, I see the problem. Is it even possible for both halves to be from the same species? Is it possible that the septa are folded in a way such that they appear concave in opposite directions throughout the thickness of the coil? The septa at the bottom of the left piece almost appears to be reversing the direction of their concavity and this would match the counterpart in the right piece: weird. Maybe this is possible if the ammonite is cut off center and parts are lost in the polishing process. Maybe we need a mathematical topologist to answer the question. My goal is to leave no stone or fossil unturned. See my Arizona Paleontology Guide link The best single resource for Arizona paleontology anywhere. Link to comment Share on other sites More sharing options...
Micah Posted February 12, 2020 Author Share Posted February 12, 2020 3 hours ago, DPS Ammonite said: Wow, I see the problem. Is it even possible for both halves to be from the same species? Is it possible that the septa are folded in a way such that they appear concave in opposite directions throughout the thickness of the coil? The septa at the bottom of the left piece almost appears to be reversing the direction of their concavity and this would match the counterpart in the right piece: weird. Maybe this is possible if the ammonite is cut off center and parts are lost in the polishing process. Maybe we need a mathematical topologist to answer the question. I’m at a loss lol out of curiosity I got my Dad to send me pictures of the ammonites he got for other family member and both seem to have the same issue. Nearly identical, but don’t actually match up. I’ll post what he sent. Link to comment Share on other sites More sharing options...
Micah Posted February 12, 2020 Author Share Posted February 12, 2020 Once again it’s beautiful, but the sides have got to be from different specimens despite being very similar. edit-sharpened and increased definition on blurry image. Link to comment Share on other sites More sharing options...
Micah Posted February 12, 2020 Author Share Posted February 12, 2020 Another one he picked up. Same issue as the other two (plus a different species). He mentioned getting a good deal. I think I know why now lol. Still they are beautiful even if they happen to not be matching halves. Must be a pretty common thing to do (at least for this seller) for 3 out of 3 to be this way. Link to comment Share on other sites More sharing options...
Wrangellian Posted February 12, 2020 Share Posted February 12, 2020 Interesting... My suspicion is that these are matching halves, but that ammonite septa are not so predictable. Remember that ammonites have very convoluted sutures, so the septa inside there would not be simple curves as they are in nautiloids. Plus, as mentioned, the saw and the polishing would tend to remove a 'kerf' of some thickness that would reduce the apparent match, and add to that the possibility of being cut little off-center. Anyway, I had never noticed this before (I guess I don't look at a lot of sliced ammonites)... Interesting how that one reverses its curve at least 2 or 3 times! 2 Link to comment Share on other sites More sharing options...
Micah Posted February 12, 2020 Author Share Posted February 12, 2020 27 minutes ago, Wrangellian said: Interesting... My suspicion is that these are matching halves, but that ammonite septa are not so predictable. Remember that ammonites have very convoluted sutures, so the septa inside there would not be simple curves as they are in nautiloids. Plus, as mentioned, the saw and the polishing would tend to remove a 'kerf' of some thickness that would reduce the apparent match, and add to that the possibility of being cut little off-center. Anyway, I had never noticed this before (I guess I don't look at a lot of sliced ammonites)... Interesting how that one reverses its curve at least 2 or 3 times! Interesting it did seem like it would be more effort than it was worth to find such exact matches lol... “an Occam’s Razor situation I do believe they were the same all along we just didn’t understand how it was possible until now my dear Watson.” I had no idea about the convoluted sutures, just assumed they would be somewhat uniform. And you know what happens when you assume... so we’re the sutures malleable then? Or just wacky shaped? Link to comment Share on other sites More sharing options...
Wrangellian Posted February 12, 2020 Share Posted February 12, 2020 They were rigid like the rest of the shell, just wacky-shaped! 1 Link to comment Share on other sites More sharing options...
Micah Posted February 12, 2020 Author Share Posted February 12, 2020 1 minute ago, Wrangellian said: They were rigid like the rest of the shell, just wacky-shaped! Interesting! Do we have any theories as to why they’re so odd? Link to comment Share on other sites More sharing options...
Wrangellian Posted February 12, 2020 Share Posted February 12, 2020 The one theory that comes to mind (maybe the only one there is), is that it's like corrugated cardboard, or rather more like the ceiling of a medieval cathedral: it provided strength to the shell, which tends to be thinner than the nautilus' shell. 1 Link to comment Share on other sites More sharing options...
Micah Posted February 12, 2020 Author Share Posted February 12, 2020 I guess while we’re at it does anyone want to take a stab at helping IDing the other two ammonites? Link to comment Share on other sites More sharing options...
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