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Ammonite ID? Perisphinctes?


JulianoLPD

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Hi there guys,
I got this ammonite as part of a set from Madagascar. 
I would like to know if this is a Perisphinctes.
What caught my attention is that it seems to be more "larger" than the regular Perisphinctes I'm used to, at least.
Let me know your thoughts.

IMG_20190712_233934.jpg

IMG_20190712_233942.jpg

IMG_20190712_233923.jpg

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I have seen them get even larger than this.

20190712_210102.jpg

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Isn't this larger one here one as well?

20190712_210617.png

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Yes! Maybe I didn't express myself properly. Sorry.
I meant it seems to be larger on the "dorsal surface". Thicker maybe...
I really don't know but it seems different from all the other ones I have.
Is it possible to ID it based on these pictures?

 

IMG_20190712_233923.jpg

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Sagebrush Steve

Here is a thread you might find useful:

 

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Yes. I do believe it is a Perisphinctes, but I think it is not the regular P. virguloides I'm used to.
I'm attaching another picture so maybe someone can give me an ID.
Thank you guys!

IMG_20190713_145900.jpg

IMG_20190713_145909.jpg

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Mark Kmiecik

Ammonites aren't my area of expertise, but size/thickness variations can be due to preservation bias.

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8 hours ago, Mark Kmiecik said:

Ammonites aren't my area of expertise, but size/thickness variations can be due to preservation bias.

I know that. But I really don't think it is the case with my specimen (though I may be wrong).

I'll add another picture that explains what I'm trying to say...

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This is what I'm trying to explain.

The first one is what I usually find to be Perisphinctes virguloides, the other one seems to be much more dorsal-ventral compressed, flattened.

Would that be an artifact of the fossilization or a different species?


Thank you all in advance

IMG_20190714_001325.jpg

IMG_20190714_001330.jpg

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Sagebrush Steve

In looking at the photo in your first post and counting the ribs in the outer whorl it is about 36, which should help define the species.  According to the paper by Gygi that I linked in my post above, most Perisphinctes species have more like 60, with some down to 40. Unfortunately that paper doesn’t include P. virguloides.  Also, your whorl cross section is much flatter than the typical Perisphinctes. Not sure if that is an artifact of the fossilization process.  So it may be a Perisphinctes but I don’t know the species.

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Mark Kmiecik

I see what you mean in the new photo -- probably not preservation bias. Overall, the two appear to be different species to me, but I am not an ammonite specialist.

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Thank you, guys! 

 

1 hour ago, Mark Kmiecik said:

I see what you mean in the new photo -- probably not preservation bias. Overall, the two appear to be different species to me, but I am not an ammonite specialist.

I guess I should've started the topic with this photo... :D

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Mark Kmiecik
18 minutes ago, JulianoLPD said:

Thank you, guys! 

 

I guess I should've started the topic with this photo... :D

I don't know -- I'm sure some of the members enjoy the mystery more if there is some detective work involved. But we still don't know if it is two species or one. Let's wait for the experts. Most of them are probably out collecting on the weekend and should be back starting tomorrow.

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On 14/07/2019 at 8:04 PM, Mark Kmiecik said:

I don't know -- I'm sure some of the members enjoy the mystery more if there is some detective work involved. But we still don't know if it is two species or one. Let's wait for the experts. Most of them are probably out collecting on the weekend and should be back starting tomorrow.

Isn't that the funny of the whole thing? :D

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