Ammonite Madagascar - Perisphinctes? Orthosphinctes?

[UtahBob]

Hi everyone,

I've been following a bit and picked up some good information on the C&D canal in Delaware recently which perked my interest in this forum. I'm really a petrified wood person but I picked up a few Ammonites from a Madagascar dealer at a local show last week. The woman there was providing the identification verbally for some of the fossils she had but when I went back at the end she was not there and I picked up some ammonites as well as polychrome jasper from her assistant. The assistant's english capacity was close to zero (the woman's was not much better) so I bagged an id figuring these were so common since I've seen them before and could get the id easily off the web. I will have to give them credit for the courage of setting up shop and doing business with the language barrier.

Well, my search seems almost impossible. I see these described as orthosphinctes and perisphinctes and I can't seem to understand what makes them either?

Once I got them back I started looking at the final chamber and for the large one, it has been cut and shows fossil material, others just show matrix and are cut also. For two of them, I think what I am seeing is the divider between the chambers - the septum. Is there a value difference between one's that have the septum visible, verses fossil matrix, verses just matrix? I recall seeing a post about someone not liking them when the final chamber is cut. I'm trying to figure out which ones to keep.

On a side note, I was also researching fakes and because of the septum I would think that these are authentic and inexpensive enough that the faking would be not worth the bother. They have a unique exterior also but I could see them being molded perhaps in larger specimens commanding higher value.

I also picked up two objects that were identified as polished goniatites but that is not what I have as you can see from the two photos. These look as they have been carved from solid material rather than cast. These were from a different dealer. These I gather are of Moroccan origin. They are a lot lighter in color than I show in the pics. One looks like it is completely tooled. I have the equipment to cut one of these cleanly in half as well as polish the cuts. If these are authentic and have just been tooled to clean them up (although the centers look (are) completely fabricated) would the cut faces show the whorl pattern even if the ammonite was completely fossilized. I would expect them to show some structure. No structure, then they are tooled or molded. Cut or no cut?

Thanks,

Bob

[caldigger]

Bob, these types of ammonites are so abundant in those locals that creating fakes would be frivolous. There might be some tool marks that the person prepping it took liberties on creating to conform to the general pattern of the scrolls, but as I said before, it wouldn't really be in there best interest to create fake common ammonites like these. I don't see anything fake or created in your pictures, all look right as rain to me.

[Aurelius]

The final (body) chamber is often missing on ammonites from certain localities, owing to the way in which they are preserved, which is why you can see a chamber divider at the end of one. It probably came out of the ground like that. The final ammonite(s?) you posted have the exact opposite problem - the body chamber filled up with sediment which hardened and protected it, but the internal chambers did not receive any deposits via the siphuncle, so it remained hollow. It was then destroyed by the weight of the rock forming on top of it.

These have the inner whorls carved in as a matter of course. I don't know how big yours is, but they do come in quite large sizes.

[UtahBob]

Thanks, I didn't expect the Madagascar ammonites to be fake but I now understand the end chamber. I think I agree, that the natural verses cut end chamber, for me, is more desirable.

Since it's been a long winter in the northeast, the cutting itch hit me and I couldn't resist slicing in half one of the two Moroccan ammonites. So from what I can tell, the fossil material is very soft. Likely limestone if not softer. Somehow, they can tell the outer dimension of the ammonite when it is removed from the ground as the outer curve approximates where the inner crystal structure shows. I thought I spotted a tad of pyritization but I'm not sure.

I'm assuming that the brown material dispersed within the ammonite is similar to the iron material in the trilobites found in Pennsylvania. Some of it appears on the outside of the ammonite and that might be an indication as to where the ammonite stops and matrix starts? That would give an indication as to where to tool?

Here are some pics. I hope cutting this doesn't break some unwritten rule regarding fossils ... it's about 5 inches across so not a big one.

[AncientEarth]

The last photo with the Moroccan one is indeed worked, often they are found with little to no remains of the center and the miners will fill in the remaining center spiral. That said, the quality shown is the standard made available aside from the abundant fakes, molded form concrete and cleaned up with chisels.

I assume if the Moroccans are not cutting them they are maybe casts or dull colors inside, I'd not seen these split, the only ones I have seen cut are from Rissani, Goulmima and Arbala which were split/polished.

**Edit** I just now saw you posted a picture of the ammonite split, very interesting! The lack of preservation must be why it's not commonly done. I always had kind of figured that they were finishing out the centers whether or not it was there or not, I've seen the same lackadaisical prep on trilobites, covering perfectly good shell for 'aesthetics'

The locality is from near Agadir, Morocco, Cretaceous in age (~112-99 Ma), and you have one which was not colored or dyed. "Finished" specimens are now dyed a rich brown or tan color for a more dramatic look.

Edited April 19, 2014 by AncientEarth

[UtahBob]

The last photo with the Moroccan one is indeed worked, often they are found with little to no remains of the center and the miners will fill in the remaining center spiral. That said, the quality shown is the standard made available aside from the abundant fakes, molded form concrete and cleaned up with chisels.

I assume if the Moroccans are not cutting them they are maybe casts or dull colors inside, I'd not seen these split, the only ones I have seen cut are from Rissani, Goulmima and Arbala which were split/polished.

**Edit** I just now saw you posted a picture of the ammonite split, very interesting! The lack of preservation must be why it's not commonly done. I always had kind of figured that they were finishing out the centers whether or not it was there or not, I've seen the same lackadaisical prep on trilobites, covering perfectly good shell for 'aesthetics'

The locality is from near Agadir, Morocco, Cretaceous in age (~112-99 Ma), and you have one which was not colored or dyed. "Finished" specimens are now dyed a rich brown or tan color for a more dramatic look.

Thanks, I am learning a lot today. Your comments confirm what Aurelius noted about the centers. I am going to a gem and mineral show tomorrow and will have to take a hard look at any specimens I come across to see if I can understand a bit better how the prep work is done.

I was never a big fan of these ammonites although I like the polished madagascar sliced ammonites ... but over the last week these two specimens have grown on me to the point I'd like to acquire a larger specimen.

I will try and polish the cut edges but only the centers are hard enough for it. Will be an interesting experiment.

[Wrangellian]

It was probably me who said I didn't like the squared-off apertures on the Madagascan ammos, but that's just me - I would pay more for a natural one, whether the living chamber was preserved or not. But I can't imagine anyone, at least any fossil specimen collector, preferring one with an artificially-cut aperture, but as I understand, the exporters do that because Madagascar law dictates that raw materials cannot be exported - they must be worked somehow. So the ammo sellers cut off the ends and that qualifies as 'value added'. I wish we had better 'value added' laws in this country but if it goes to this extreme it has gone too far! Of course you show there are some with natural ends, I'm not sure how they get out, but I'm glad. I do have a couple with cut ends but that's only because that's all that was available and they were cheap (better than nothing if you're aiming for anything like a 'complete set'). I will replace them if I can find better, more natural ones.

I'm glad you sliced that one to see the inside - I had my doubts that ammo was legit because of the poor prep job that made it look like the whole thing was carved out of raw rock (which I've seen among Moroccan wares). It may be real (except for the reconstructed inner whorls) but I would have avoided it just because of that prep job.

This thread might be a good addition to the 'How to spot fakes' topic.

I am not sure how to ID these -sphinctes varieties either so I will watch to see if someone else does.

[UtahBob]

It was probably me who said I didn't like the squared-off apertures on the Madagascan ammos, but that's just me - I would pay more for a natural one, whether the living chamber was preserved or not. But I can't imagine anyone, at least any fossil specimen collector, preferring one with an artificially-cut aperture, but as I understand, the exporters do that because Madagascar law dictates that raw materials cannot be exported - they must be worked somehow. So the ammo sellers cut off the ends and that qualifies as 'value added'. I wish we had better 'value added' laws in this country but if it goes to this extreme it has gone too far! Of course you show there are some with natural ends, I'm not sure how they get out, but I'm glad. I do have a couple with cut ends but that's only because that's all that was available and they were cheap (better than nothing if you're aiming for anything like a 'complete set'). I will replace them if I can find better, more natural ones.

I'm glad you sliced that one to see the inside - I had my doubts that ammo was legit because of the poor prep job that made it look like the whole thing was carved out of raw rock (which I've seen among Moroccan wares). It may be real (except for the reconstructed inner whorls) but I would have avoided it just because of that prep job.

This thread might be a good addition to the 'How to spot fakes' topic.

I am not sure how to ID these -sphinctes varieties either so I will watch to see if someone else does.

Wow, this is a great forum of information.

I found 2 completes out of the 19 I picked up which varied in size from 3 inches to half and inch. I should have gone through the entire lot in the box to look for the completes but I didn't realize they existed.

This "working" the material for export makes a lot of sense now. All the Madagascar petrified wood is polished or cut and polished. Even the geodes that came out recently. I wondered about why they were all cracked in half and then rubber banded.

The best way to spot a fake in my book is the price. If it looks low, then you start to question it, and don't buy anything for decent $ if you don't know anything about it. My first experience with semi-fakes was at the fossil co-op in Tucson on Oracle. I was talking to the folks at Sahara Seas and they were explaining to me how the moses jaws and teeth were real but the assemblage in the matrix was man made.

[Wrangellian]

I am not sure I have ever seen a truly complete Madagascan ammo, mostly they are either squared off or broken at one of the septa, like your example. If you find one with the living chamber and the original aperture, grab it.

As long as you know what something should be priced at, the price might be a good indicator.

[UtahBob]

I am not sure I have ever seen a truly complete Madagascan ammo, mostly they are either squared off or broken at one of the septa, like your example. If you find one with the living chamber and the original aperture, grab it.

As long as you know what something should be priced at, the price might be a good indicator.

I did not manage to find any ammos at the show yesterday with a a living chamber or original aperture. In fact, i'm more confused on the original question of perisphinctes verses orthosphinctes as one I saw yesterday was labeled something different but it was in poor shape so I discounted the id.

I also broke some of my rules on buying and not knowing what something should be priced at as you noted. I picked up a small peruvian sea urchin and a 137 gm pyritized jumble of what I think are Crucilobiceras and Oxynoticeras from Charmouth UK based on some research last night. The two types on one plate seemed unusual so I went for it. Similarly a week ago I picked up some Isurus and a fractured Megladon. I will have to post the pyrite plate, the Isurus and the Megladon in separate threads.

[Wrangellian]

I guess you can break the 'rules' for smaller, cheaper items - won't break the bank if it turns out to be fake or worth even less than you paid! I'm sure I have bought things on spec (or hunch) too...

I have seen what appear to be 2 different types of -sphinctes from there.. they have slightly different cross-sections, one is more squarish, I can see them in your pics above - but again I'm not sure which is which, nor whether there are more than 2.

Edited April 21, 2014 by Wrangellian