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Phyllocarid carapace, trilobite, or possibly a brachiopod?


Cassandra Tiensivu

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Hello everyone. I’ve been chiseling apart some of my less than fabulous Mississippian Coldwater Shale packstones that I find in South Haven (MI) on Lake Michigan. Typically, I’ll discover various brachiopods, a few gastropods, various bryozoan, some ostracods, and little bits of flora that look like tiny seaweed.

 

However, recently I opened up a packstone with a very different fossil inside. I have nothing else like it in my collection. A few folks I know have speculated the things I mentioned in the title of this post. 
 

The second picture is... I guess I would call it a cast? 
 

The third picture is the interior of the shell of whatever this creature was. 



 

 

C9EB8204-FE0A-414F-BA29-B35AD10AE17E.jpeg

25FBA675-5AC9-48A5-8C0A-8049CE1D0C02.jpeg

F2A932CB-0B2E-4345-8DF6-49C43236A987.jpeg

25572F4B-A375-4C0C-AFD8-52702F492A0B.jpeg

D8E3A66D-0AAC-4911-98BA-6762CE41BC68.jpeg

Edited by Cassandra Tiensivu
Added two macro photos.
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Any chance of further prep?

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“If fossils are not "boggling" your mind then you are simply not doing it right” -Ken (digit)

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I'm getting a trilobite cephalon vibe on this one. :unsure: 

 

Something like Ameura major

 

6a0105351bb26c970c0263e9564941200b-500wi.jpg   25FBA675-5AC9-48A5-8C0A-8049CE1D0C02.thumb.jpeg.33e2db6d33a0c08825b62ac68bbbdbb3.jpeg

 

 

@piranha

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Just now, Fossildude19 said:

I'm getting a trilobite cephalon vibe on this one. :unsure: 

 

@piranha

That's my first impression too, but is there a large enough Mississippian one?

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Tarquin

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5 minutes ago, Top Trilo said:

Any chance of further prep?


I’m a super newbie when it comes to fossil prep. And, if this piece follows suit in fragility with the brachiopods in these stones, it’s going to be fragile. I’m afraid I’d damage it. 

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45 minutes ago, Fossildude19 said:

I'm getting a trilobite cephalon vibe on this one. :unsure: 

 

Something like Ameura major

 

6a0105351bb26c970c0263e9564941200b-500wi.jpg   25FBA675-5AC9-48A5-8C0A-8049CE1D0C02.thumb.jpeg.33e2db6d33a0c08825b62ac68bbbdbb3.jpeg

 

 

@piranha

 

Yeah. That looks like part of the head, right? 
 

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16 minutes ago, Cassandra Tiensivu said:

 

Yeah. That looks like part of the head, right? 
 

Yeah the cephalon is the trilobite head

“If fossils are not "boggling" your mind then you are simply not doing it right” -Ken (digit)

"No fossil is garbage, it´s just not completely preserved” -Franz (FranzBernhard)

"With hammer in hand, the open horizon of time, and dear friends by my side, what can we not accomplish together?" -Kane (Kane)

"We are in a way conquering time, reuniting members of a long lost family" -Quincy (Opabinia Blues)

"I loved reading the trip reports, I loved the sharing, I loved the educational aspect, I loved the humor. It felt like home. It still does" -Mike (Pagurus)

“The best deal I ever got was getting accepted as a member on The Fossil Forum. Not only got an invaluable pool of knowledge, but gained a loving family as well.” -Doren (caldigger)

"it really is nice, to visit the oasis that is TFF" -Tim (fossildude19)

"Life's Good! -Adam (Tidgy's Dad)

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28 minutes ago, Top Trilo said:

Yeah the cephalon is the trilobite head


Ah hah. Thank you for that! Though I’ve long admired them from afar, I haven’t found any previously. I’m going to assume figuring out a specific species is pretty much out of the question with how little of the fossil I actually have here, right? 

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1 hour ago, Fossildude19 said:

Something like Ameura major

 

1 hour ago, TqB said:

That's my first impression too, but is there a large enough Mississippian one?

 

Yes, Carboniferous trilobites could attain a maximum size up to 5 cm or larger. This one is superficially similar to Ameura missouriensis but that species is not reported from Michigan. Trilobites from the families Phillipsiidae and Proetidae have been described from the Mississippian of Michigan. Unfortunately there is not enough detail preserved to ID beyond: Order Proetida indet.

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image.png.a84de26dad44fb03836a743755df237c.png

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Here's a faunal list of Kinderhookian trilobites from Coldwater Shale equivalents. It's pretty dated, though:

Hessler, Robert R. “Lower Mississippian Trilobites of the Family Proetidae in the United States, Part II.” Journal of Paleontology, vol. 39, no. 2, 1965, pp. 248–264. JSTOR, www.jstor.org/stable/1301689. Accessed 13 Apr. 2021.

 

Lower Miss Trilobites.pdf

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Great specimen and discussion. 
 

Taking responsibility for being the one who originally suggested phyllocarid as a possibility... here is a reference specimen that had me thinking along such lines. It’s from the following FF thread: http://www.thefossilforum.com/index.php?/topic/83763-phyllocarid-collection/

 

2DE3229D-3BE7-4354-B1DD-C78B39C4F416.jpeg

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2 hours ago, LisaL said:

Here's a faunal list of Kinderhookian trilobites from Coldwater Shale equivalents. It's pretty dated, though:

Hessler, Robert R. “Lower Mississippian Trilobites of the Family Proetidae in the United States, Part II.” Journal of Paleontology, vol. 39, no. 2, 1965, pp. 248–264. JSTOR, www.jstor.org/stable/1301689. Accessed 13 Apr. 2021.

 

 

The first installment of Hessler has the formal description of Pudoproetus michiganensis from the Coldwater Shale of Huron & Branch Counties:

 

Hessler, R.R. 1963. Lower Mississippian Trilobites of the Family Proetidae in the United States, Part I. Journal of Paleontology, 37(3):543-563

 

image.png.d3600e89bac4880f3a50133adf7265a7.png

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The ribbing on piranha’s image of Pudoproetus michiganensis more matches the ribbing on my specimen than the phyllocarid. But, it was definitely worth looking into! I’ll make a note of that species and keep the image tucked away in case I ever come across something like that in the future. 
 

Comparing my piece to the photo of Pudoproetus michiganensis that piranha posted (with some tweaks to the contrast to bring out the ribbing visibility more), if you remove the eyeball from the black and white fossil, seems like a pretty good match to mine. 

830ADB48-C327-45B7-9A39-865F808DA95F.jpeg

Edited by Cassandra Tiensivu
Adding a photo and following up with some comments about it.
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Does there happen to be anymore info out there on Pudoproetus michiganensis? My internet search results had hardly anything come up. 

 

Thank you all for your help! It’s been most appreciated. 

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image.thumb.png.3dba3495aabbca598f098f95e5f10de1.png

 

Hessler, R.R. 1963. Lower Mississippian Trilobites of the Family Proetidae in the United States, Part I. Journal of Paleontology, 37(3):543-563

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