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Mainefossils
Posted (edited)

So, I have been preparing this nice little gastropod. I have seen five other specimens that shared the same characteristics, but, unfortunately, some of them did not make it. Before I continued to prep this one, I was wondering if it is possible to roughly ID this gastropod. It would greatly facilitate prep work to have a good idea of its shape.

 

All the specimens I have seen have had three whorls. The upper two whorl's ridges are almost absent, this has been consistent through all my specimens. The shape of the shell is coeloconoid. 

 

It was found in the Leighton Formation, Maine; which is Pridoli, Silurian. The pictures below are of the specimen under direct, then raking light. The third picture is the external mold under direct light.

 

Thanks in advance for your help!

 

@MikeR @Rockwood

 

381855044_gastropod1.thumb.jpg.804db82b259641132c7f497665628e58.jpg

 

80482711_gastropd2.thumb.jpg.f90cd8c3204f369f7e3af7319379a8f9.jpg

 

182503220_gastropod3.thumb.jpg.0af635e44c0d7b0b9cfbbf5324f33ff9.jpg

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doushantuo

Maine ,you can still edit the title("Gastopod""}

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  • Mainefossils changed the title to Gastropod ID
Mainefossils
5 minutes ago, doushantuo said:

Maine ,you can still edit the title("Gastopod""}

:DOH: Thanks! 

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cngodles
Posted (edited)

This has a Shansiella vibe, but that doesn't fit with the time period.

 

But wow does Australonema sp. look EXACTLY like Shansiella. As I understand now is an example of convergent evolution.

https://www.researchgate.net/publication/228667498_Silurian_Gastropoda_from_Southeastern_and_West-Central_Alaska

 

image.png.db0fc21c542395a65e9bd204661d75f4.png

 

Also, yours appears skewed, so the spire may be deceivingly high.

Edited by cngodles
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Mainefossils
57 minutes ago, cngodles said:

This has a Shansiella vibe, but that doesn't fit with the time period.

 

But wow does Australonema sp. look EXACTLY like Shansiella.

https://www.researchgate.net/publication/228667498_Silurian_Gastropoda_from_Southeastern_and_West-Central_Alaska

 

image.png.db0fc21c542395a65e9bd204661d75f4.png

I think that you have got it. Australonema is known from the Silurian of the USA. As I have researched it, though, I have not found many instances of this genus here. It could be something closely related. 

 

From what I have read, there are only two other genera in this family that are found in the USA, HecetastomaOriostoma. I have not found a single occurrence of either of these genera in the Leighton Formation, or for that matter, in Maine. 

 

58 minutes ago, cngodles said:

Also, yours appears skewed, so the spire may be deceivingly high.

 

The reason that I thought that this shell was coeloconoid was because of an earlier specimen. I would show you pictures, but unfortunately it disintegrated before I could consolidate it. 

 

Thanks for your help! :)

 

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Rockwood

I don't think enough notes have been heard yet to guess the song. :)

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  • 4 weeks later...
Mainefossils
Posted (edited)

I have just found another gastropod that seems to fit the bill pretty well. It is not listed as being found specifically in this formation, but it is found in the Silurian Edmunds formation, that is right next to the Leighton. It is the genus Cyclonema. The plate below shows the type species, C. bilex, in figures A - D. 

                                                                       1110211782_ScreenShot2021-07-31at3_44_09PM.png.2c9ccd3038b86405afa1b0a90375c980.png

Lucas, S. G., Hunt, A. P., Lichtig, A. J. (2021) Fossil Record 7. New Mexico Museum of Natural History and Science Bulletin, 82. 

https://books.google.com/books?hl=en&lr=&id=DLoxEAAAQBAJ&oi=fnd&pg=PA341&dq=cyclonema+bilex+gastropod+&ots=a-mmD6h0FJ&sig=5V4yanxBUSURHbADWw5R7uAtA84#v=onepage&q&f=false

 

I also found a separate paper, namely:

 

Peel, J. S. (1973) A Silurian Gastropod Fauna from the Arisaig group of Nova Scotia

https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.737234

 

In plates IX and X, C. lydiamarium and C. parvimedium are shown. My specimen shows some of the same ornamentation and structure of these specimens, although I doubt mine can be identified to species reliably. 

 

Thoughts @cngodles?

 

 

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cngodles

I would say figured E-F fit better. It's really the corded structure on the last whorl that have me aimed at something like Australonema.

 

That certainly doesn't mean I'm right. The specimen also looks skewed like butter spread over bread. I have at least one Shansiella like that. This creates the illusion that the spire is higher than what it would be un-morphed. Example below:

144.jpg

CG-0144 - Shansiella carbonaria

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Mainefossils
Posted (edited)

Thanks for your opinion @cngodles

 

I see what you mean with figures E - F, which is an unidentified Cyclonema sp . Sorry, I forgot to put the link for the paper - it is edited now. I certainly understand what you mean with Australonema and related - I am just trying to find something that is known from Maine, and fits all the morphological features that this specimen shows.  

 

Thanks for your patience! :)

 

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cngodles

Also Australonema lacks a selenizone, which you specimen also seem to lack.


Attached is an illustration of the type for the entire genus: Cyclonema Australia.

 

References:


http://fossilworks.org/bridge.pl?a=taxonInfo&taxon_no=8582

 

https://media.australian.museum/media/Uploads/Journals/16617/1227_complete.pdf

8DE903F2-D5F4-44A7-A1A5-3F016AA5F3BD.jpeg

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Mainefossils

@cngodles, very interesting.

 

I really think that you are right. I did not realize that the type species is A. australis, which used to be classified as a Cyclonema. Also, the fossils from the Edmunds and Leighton Formation have not been significantly researched recently, so Cyclonema species from these formations may in fact be in the genus Australonema. I think that this gastropod could be considered an unidentified Australonema (=Cyclonema) sp. 

 

Thank you so much for your help! This is really interesting to me, and I appreciate you taking the time to research this. :)

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  • 2 weeks later...
cngodles

I do want to make a correction here. I no longer think that CG-0144 is Shansiella carbonaria. This is irrelevant to this conversation as a whole, but in general it is much too large in my opinion to be one. I did a comprehensive study on the species Shansiella carbonaria, and when I was making plates, I examined everything I had and this thing is just way too big. It can be seen at this link in comparison with the rest.

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