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Tidgy's Dad

Here is another specimen from the Southgate Hill road cut near St. Leon, Indiana. So it is Richmondian, Cincinnatian, Late Ordovician in age, Upper Arnheim, Waynesville, or Liberty Formations found in a rock with multiple Strophomena planumbona, lots of tiny ramose bryozoan fragments and some crinoid columnals. 

At first I thought it was an echinoderm of some ilk, but now I'm leaning towards a fragment of the bivalve Caritodens welchi like the one Ralph @Nimravisposted in this thread

 

The bit I have is about a centimetre long and 1.5 mm wide. 

Thank you, as always, for any suggestions.

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N.B. This specimen was also sent to me by Ralph. Thanks again, my friend. 

@erose @connorp

Thanks, everyone. 

 

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connorp

My initial reaction is that this is a fragment of the monoplacophoran Phragmolites.

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Tidgy's Dad
1 hour ago, connorp said:

My initial reaction is that this is a fragment of the monoplacophoran Phragmolites.

Good call. 

Phragmolites dyeri is found in this location and I think that's a closer match and not something I'd looked at.

Though they are still arguing whether the Bellerophontida are monoplacophorans or gastropods, I think they're currently gastropods. For now.

Thank you very much. :SlapHands:

 

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ClearLake

image.png.e68b9d18239fcb7d354b52f91d3f7896.png

 

@connorp beat me to it, but it does indeed look like a piece of Phragmolites dyeri.  Here is a picture of one I took off of the Dry Dredgers website and you can see the distinctive "S" shaped ornamentation by the aperture.

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Crusty_Crab

Based on this website, there are other species of Phragmolites in the Cincinnatian: https://strata.uga.edu/cincy/fauna/gastropoda/Phragmolites.html 

Phragmolites dyeri (Hall, 1872) is found in the Waynesville and Liberty Formations, but does anyone know how to differentiate the species other than their occurrence? For example, here is one of my own finds in the Platteville Formation of Wisconsin:

 

ELL190918004-3.thumb.jpg.db1436e4449371ce62b461e492842817.jpg

 

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Tidgy's Dad
4 hours ago, Crusty_Crab said:

Based on this website, there are other species of Phragmolites in the Cincinnatian: https://strata.uga.edu/cincy/fauna/gastropoda/Phragmolites.html 

Phragmolites dyeri (Hall, 1872) is found in the Waynesville and Liberty Formations, but does anyone know how to differentiate the species other than their occurrence? For example, here is one of my own finds in the Platteville Formation of Wisconsin:

 

Not a clue, I'm afraid. 

But yours is a lovely specimen. :)

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4 hours ago, Crusty_Crab said:

Based on this website, there are other species of Phragmolites in the Cincinnatian: https://strata.uga.edu/cincy/fauna/gastropoda/Phragmolites.html 

Phragmolites dyeri (Hall, 1872) is found in the Waynesville and Liberty Formations, but does anyone know how to differentiate the species other than their occurrence? For example, here is one of my own finds in the Platteville Formation of Wisconsin:

 

ELL190918004-3.thumb.jpg.db1436e4449371ce62b461e492842817.jpg

 

You need to find any published faunal lists for the Platteville and check if any of the Cinci species occur there as well.  It certainly appears to be the same genus but the ornamentation is slightly different. 

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connorp
7 hours ago, Crusty_Crab said:

Based on this website, there are other species of Phragmolites in the Cincinnatian: https://strata.uga.edu/cincy/fauna/gastropoda/Phragmolites.html 

Phragmolites dyeri (Hall, 1872) is found in the Waynesville and Liberty Formations, but does anyone know how to differentiate the species other than their occurrence? For example, here is one of my own finds in the Platteville Formation of Wisconsin:

 

ELL190918004-3.thumb.jpg.db1436e4449371ce62b461e492842817.jpg

 

The two Platteville species are P. fimbriatus and P. triangularis. See here:

https://equatorialminnesota.blogspot.com/2020/02/phragmolites.html

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ClearLake

 

On 3/7/2021 at 3:54 PM, Crusty_Crab said:

Based on this website, there are other species of Phragmolites in the Cincinnatian: https://strata.uga.edu/cincy/fauna/gastropoda/Phragmolites.html 

Phragmolites dyeri (Hall, 1872) is found in the Waynesville and Liberty Formations, but does anyone know how to differentiate the species other than their occurrence?

From the 1996 USGS Publication 1066-O it says: "P. dyeri is readily distinguished from P. bellulus and P. elegans by its more cordate shaped aperture, its more closely spaced lamellae, its prominent spiral threads, and the absence of lunulae on its selenizone."

 

I think the spiral threads that are referenced are easy to see in the specimen I posted from the Dry Dredgers website, but less easily seen in Adams  specimen due to the partial nature of the fossil and the preservation.  I agree that based on the partial fossil Adam has, it may be difficult to definitively assign one of the three species found in the Cincinnatian Series, but apparently the various species are only found in specific formations, so that is a big help.

 

The reference listed does not address the species found in the Platteville, so unfortunately @Crusty_Crab I can't help you there, but hopefully the other replies have provided some guidance.

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Crusty_Crab
On 3/7/2021 at 5:30 PM, Tidgy's Dad said:

Not a clue, I'm afraid. 

But yours is a lovely specimen. :)

Thanks!

 

On 3/7/2021 at 6:06 PM, erose said:

You need to find any published faunal lists for the Platteville and check if any of the Cinci species occur there as well.  It certainly appears to be the same genus but the ornamentation is slightly different. 

Looks like they are not, but as with species that have been described +100 years ago, with unclear holotypes and enthusiastic naming sprees, the fauna would benefit from a modern re-evaluation and reorganization.

 

On 3/7/2021 at 9:35 PM, connorp said:

The two Platteville species are P. fimbriatus and P. triangularis. See here:

https://equatorialminnesota.blogspot.com/2020/02/phragmolites.html

 

On 3/7/2021 at 10:18 PM, connorp said:

While we're on the topic, there is a very useful faunal list for Platteville mollusks in the 2010 MAPS Expo Digest.

http://www.midamericapaleo.org/content/EXPO/Digests/EXPO_Digest_2010_Final.pdf

Thanks, those are very helpful. I was able to download Ulrich and Schofield's massive volume from 1891, which appears to be the key publication.

 

19 hours ago, ClearLake said:

 

From the 1996 USGS Publication 1066-O it says: "P. dyeri is readily distinguished from P. bellulus and P. elegans by its more cordate shaped aperture, its more closely spaced lamellae, its prominent spiral threads, and the absence of lunulae on its selenizone."

 

I think the spiral threads that are referenced are easy to see in the specimen I posted from the Dry Dredgers website, but less easily seen in Adams  specimen due to the partial nature of the fossil and the preservation.  I agree that based on the partial fossil Adam has, it may be difficult to definitively assign one of the three species found in the Cincinnatian Series, but apparently the various species are only found in specific formations, so that is a big help.

 

The reference listed does not address the species found in the Platteville, so unfortunately @Crusty_Crab I can't help you there, but hopefully the other replies have provided some guidance.

Which publication is the USGS 1996 1066-0? I'm not sure I know that one.

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ClearLake

 

1 hour ago, Crusty_Crab said:

Which publication is the USGS 1996 1066-0? I'm not sure I know that one.

https://pubs.er.usgs.gov/publication/pp1066O

 

The US Geological Survey did a whole series of publications in the 80's and 90's on the Ordovician of the Cincinnati Arch.    They are usually on a particular group of fossils such as this one on certain uni-valved mollusks.  All free to download.

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Tidgy's Dad

Thanks everyone! 

Not only did I get my id, but some really useful information and nice photos of specimens too. :i_am_so_happy:

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