JulianoLPD Posted March 16, 2019 Share Posted March 16, 2019 Hi there folks, me again. =) I'm having a pretty ocious day, so I'm spending my time taking a look at my unidentified pieces. I was hoping if someone can help me with these specimens. They are both from Madagascar so I'm thinking Aioloceras besairiei... Could that be right? In case I'm right, what about this color pattern? Can we figure out about the mineralization process? Finally, ammonoids from Madagascar are generally A. besairiei? Thanks in advance, Juliano 1 Link to comment Share on other sites More sharing options...
ziggycardon Posted March 16, 2019 Share Posted March 16, 2019 Actually this is a fossil nautilus and not an ammonite The species I think is Cymatoceras sp. 5 Interested in all things paleontology, geology, zoology, evolution, natural history and science! Professional exotic pet keeper, huge fantasy geek, explorer of the microfossil realm, member of the BVP (Belgian Association for Paleontology), Volunteer prepper at Oertijdmuseum Boxtel. View my collection topic here: The Growing Collection of Ziggycardon My animal collection at the "Members pet" topic Ziggycardon's exploration of the microfossil realm Trips to Eben Emael (Maastrichtian of Belgium) My latest fossil hunt Next project will be a dedicated prepping space. "A mind needs books as a sword needs a whetstone, if it is to keep its edge." - Tyrion Lannister Link to comment Share on other sites More sharing options...
ziggycardon Posted March 16, 2019 Share Posted March 16, 2019 Here for a quick real life comparison. The above is my specimen of a nautilus The two specimens below are Aioloceras besairiei ammonites, the right one is polished so you can see the suture lines well. I hope this was helpfull to you! 1 Interested in all things paleontology, geology, zoology, evolution, natural history and science! Professional exotic pet keeper, huge fantasy geek, explorer of the microfossil realm, member of the BVP (Belgian Association for Paleontology), Volunteer prepper at Oertijdmuseum Boxtel. View my collection topic here: The Growing Collection of Ziggycardon My animal collection at the "Members pet" topic Ziggycardon's exploration of the microfossil realm Trips to Eben Emael (Maastrichtian of Belgium) My latest fossil hunt Next project will be a dedicated prepping space. "A mind needs books as a sword needs a whetstone, if it is to keep its edge." - Tyrion Lannister Link to comment Share on other sites More sharing options...
abyssunder Posted March 16, 2019 Share Posted March 16, 2019 ...or maybe Cenoceras ? link 3 " We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. " Thomas Mann My Library Link to comment Share on other sites More sharing options...
Ludwigia Posted March 16, 2019 Share Posted March 16, 2019 It's definitely a nautilus, either Cymatoceras or Cenoceras. It's not possible to determine which, since the shell with the diagnosic ribs have neen polished away. The only way to know would be to find out the stratigraphy. If it's Cretaceous or Late Jurassic, then it's Cymatoceras. If it's Early or Middle Jurassic, then it's probably a Cenoceras, although there was a bit of cross-over in the late Middle Jurassic where the Cymatoceratidae developed out of the Cenoceratidae. 6 Greetings from the Lake of Constance. Roger http://www.steinkern.de/ Link to comment Share on other sites More sharing options...
JulianoLPD Posted March 16, 2019 Author Share Posted March 16, 2019 Thank you, guys! That's extremely helpful! I've already heard about the differences between them, but I've seen cephalopods with straight sutures being treated as ammonoids. So I was a bit uncertain about how to differentiate them. I believe the position of the siphuncule would easily separate them, but it is hard to find a specimen with visible siphuncule... So, are my specimens polished to the internal sutures or that is their external appearance? Also, so I don't miss any more, this halved cephalopods are actually nautiloids then, tight? Link to comment Share on other sites More sharing options...
Ludwigia Posted March 16, 2019 Share Posted March 16, 2019 2 hours ago, JulianoLPD said: Thank you, guys! That's extremely helpful! I've already heard about the differences between them, but I've seen cephalopods with straight sutures being treated as ammonoids. So I was a bit uncertain about how to differentiate them. I believe the position of the siphuncule would easily separate them, but it is hard to find a specimen with visible siphuncule... So, are my specimens polished to the internal sutures or that is their external appearance? Also, so I don't miss any more, this halved cephalopods are actually nautiloids then, tight? As already mentioned above, your first specimen shows the internal and not the external structure. Nautilus siphuncles run through the middle of the phragmocone, ammonite siphuncles lie just under the keel. For this reason I suspect that your second specimen is an ammonite rather than a nautilus. Some ammonites really do have this simpler form of septa. Please show us the reverse side of this specimen. Now it's getting complicated, isn't it? 1 Greetings from the Lake of Constance. Roger http://www.steinkern.de/ Link to comment Share on other sites More sharing options...
JulianoLPD Posted March 17, 2019 Author Share Posted March 17, 2019 Yes, that's what made me confuse. I would be able to see the siphunculs in a halved Nautiloid, right? But this halved one has no visible siphuncule, but sutures are pretty straight... I believe the outer surface have been polished but here it goes. P.S. Can anyone send a picture of a halved nautiloid? Link to comment Share on other sites More sharing options...
Aurelius Posted March 17, 2019 Share Posted March 17, 2019 2 hours ago, JulianoLPD said: Thank you, guys! That's extremely helpful! I've already heard about the differences between them, but I've seen cephalopods with straight sutures being treated as ammonoids. So I was a bit uncertain about how to differentiate them. I believe the position of the siphuncule would easily separate them, but it is hard to find a specimen with visible siphuncule... So, are my specimens polished to the internal sutures or that is their external appearance? Also, so I don't miss any more, this halved cephalopods are actually nautiloids then, tight? Those are ammonites. 1 Link to comment Share on other sites More sharing options...
JulianoLPD Posted March 17, 2019 Author Share Posted March 17, 2019 18 minutes ago, Aurelius said: Those are ammonites. That's pretty confusing now... lol How can you tell? By the absence of siphuncule? Link to comment Share on other sites More sharing options...
Aurelius Posted March 17, 2019 Share Posted March 17, 2019 They're just very distinctive. Here's a nautilus for comparison (not my image). 1 Link to comment Share on other sites More sharing options...
JulianoLPD Posted March 17, 2019 Author Share Posted March 17, 2019 1 hour ago, Aurelius said: They're just very distinctive. Here's a nautilus for comparison (not my image). Thank you very much! That's what I was looking for! So we can see the siphuncule inside the nautiloids, and not all ammonoids have complex internal sutures! Thank you all guys! Link to comment Share on other sites More sharing options...
andreas Posted March 17, 2019 Share Posted March 17, 2019 17 hours ago, JulianoLPD said: So we can see the siphuncule inside the nautiloids, and not all ammonoids have complex internal sutures! Thank you all guys! None ammonite is showing complex intern sutures. The most complex suture is directly beneath the ammonoid shell. The deeper you grind/polish the less complex the suture gets. By cutting in the middle, every ammonoid looks similar(of course not exactly) a nautiloid. As said above the position of the siphuncle is a way to difference. If you look close to your cut specimen you can see on the outer edges of your sliced ammonoid specimen some roundish things. That are parts of the complex suture lines of ammonites. The link is showing(google search) a three dimensional suture structure. It is easier to imagine then. 3 Link to comment Share on other sites More sharing options...
JulianoLPD Posted March 18, 2019 Author Share Posted March 18, 2019 Wow! That's is amazing! Thank you for that info. Now I get it. Thank you very much! Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now