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ID help, Maclurites?


fourfourtwo

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Hi All,

 

Wondering if I can get some ID help with this, after reviewing various sources I am thinking Maclurites?

 

Location: Belvedere Quarry (ESCONI trip 2020) Dolomite, Galena formation

 

Thank you!

 

 

 

 

Maclurites fossil.jpg

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I'm thinking Liospira sp. based on those umbilical ridges. Liospira is a pretty characteristic fossil of the Galena Group in Illinois.

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Liospira spiral clockwise. Maclurites is counterclockwise. This suggests maclurites to me but I also saw the ridges that @Thomas.Dodson did,  which is uncharacteristic for maclurites.

 

 Mike

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16 minutes ago, minnbuckeye said:

Liospira spiral clockwise. Maclurites is counterclockwise. This suggests maclurites to me but I also saw the ridges that @Thomas.Dodson did,  which is uncharacteristic for maclurites.

 

 Mike

In modern gastropods reverse coiling in a species is known. I remember one of my old professors (a big macroinvertebrate buff) found it pretty fascinating. There's no reason to think it couldn't happen in the fossil record. I don't have enough experience with Maclurites and Liospira to say which is more likely; a reverse coiled Liospira or a ridged Maclurites. Link to reverse coiling literature with multiple references

 

I will add this statement from the paper The Platteville and Galena Groups in Northern Illinois (H. B. Willman and Dennis R. Kolata. 1978.) "Although the gastropod Maclurites is locally common in the Stewartville Member of the Wise Lake Formation in northeastern Iowa and southeastern Minnesota, it is relatively uncommon in northern Illinois.". In contrast it mentions how Liospira is characteristic of the group in Northern Illinois. While Maclurites obviously can't be ruled out with this it's still worth mentioning.

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Another differentiating feature is SIZE. Most Liospira are under half dollar size. Maclurites are typically much larger. It would help to know the specimen dimensions as a way to help with likely ID.

  

Mike

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Thanks for all the input and information. The size is definitely less than a half dollar, it is approximately an inch in diameter. 

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