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Iowa Devonian Fossil Help Please


DavidA

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Found this fossil recently while visiting the Fossil Park near Rockford, Iowa. The fossils here are Devonian in age, and belong to the Hackberry Group/Lime Creek Formation. Have found numerous varieties of brachiopods, horn and colony coral, gastropods, bryozoa, and pieces of crinoid stems, but have never seen anything quite like this. Since it was such a crappy day, I had the whole park to myself except for one guy from Minnesota. Thinking he might be more knowledgeable than myself, I asked for his opinion on what he thought this was. He suggested it was definitely a crinoid calyx. I am not so sure.

Thank you all for checking it out.

 

IMG_0864.thumb.jpg.50e160f2eb2e397065422150cb7c9577.jpgIMG_0866.thumb.jpg.41ace797571f229a22c16e796b74a961.jpgIMG_0870.thumb.jpg.018a75d20ad2a0475919da89623a366f.jpgIMG_0871.thumb.jpg.1e71070274cb17a8fa10a61a396eccff.jpgDigMicro1.thumb.jpg.32b3dae9fcb3e1a5cf35d0ef457fadac.jpgDigMicro2.thumb.jpg.2811772ace746d9db780f64ecd6ae030.jpg

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Great photos! I would love to see a bit more of the matrix peeled away where the specimen becomes narrower (but not at the very extreme tapered point). My initial guess would be a high-spired gastropod.

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I agree it is a gastropod.  The fellow you talked to may have been misled by the patterns on the surface that superficially resemble stellate ornament one might see on a crinoid.

 

Don

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Thanks for all the feedback guys!!

Is it unusual for the end segment to be larger than the proceeding one, or am I looking at it wrong? The little curly "tail" has me confused.

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I am thinking that "tail" is the last whorl that encompasses the aperture. As you proceed away from that, the whorls get smaller. 

 

Although this is not in any way a species match, figure b in this image show the general design:

 

Paleozoic-Perunelomorpha-A-G-and-Caenoga

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  • 1 month later...

Im not surprised no one got the answer. Resources for Iowa fossils is very limited. I only got a book and papers from a field trip to Rockford. This is Westerna pulchra and you wont find any pics or details online. Uncommon to rare for me. I only had two positive id compare to more than 10 Westerna gigantea with Holopea iowensis the most common at more than 40 speciments. And that doesnt includes common bellerophon, uncommon straparollus. Westerna pulchara looks the most modern looking salt water out of all the shells, almost like some small conch or triton. 

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After all its amazing how species Id is still so primitive. There's not a single book that had 100% id of Florida shallow water seashell species (of modern era) and that doesn't even includes the Keys which certain varieties or species are limited to an tiny range. 

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26 minutes ago, Tetradium said:

This is Westerna pulchra and you wont find any pics or details online.

"Challenge accepted."

 

Bensbergia (Westernia) pulchra (Bensbergia according to P. J. Wagner. 2020. Paleozoic Gastropod, Rostroconch, Helcionelloid and Tergomyan Database (2006 - 2020).)

 

Originally described: Fenton, C.L., and Fenton, M.A., 1924, The stratigraphy and fauna of the Hackberry stage of the Upper Devonian: University of Michigan, Museum of Geology Contributions, v. 1, 260 p. 

PDF LINK

 

I love these days where old publications are digitized. I'm young but I still remember having to get paper copies of manuscripts from a library and run them through a photocopier. 

westernia.png.4e062d15bfb80ea4c8f831483a3bf03e.png

Westernia2.png.f43980d9f18b26dd6625324e9740cd59.png

Westerna.png.ae69cde4c7cfbf192e4a5ffe4dba804b.png

Westerna2.png.4eac843e39da75c2f55a76b46a575930.png

 

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I miss those old days as well too. Everything is copyrighted. At least that explained why Westerna is so rare online. After all 2020 means the newest name interesting. That means theyre finally starting to sort through devonian consider brachiopods taxonomy seem to be mixed up. 

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Heres a group I labelled Straparollus sp. They look different but then again cast molds are sensitive to disortions. 

100_8862 (2).jpg

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Here are what i labeled Holopea iowensis. There might be a few other genus hidden in this batch. I like to think of them as apple snail for a while but top shell is more like it. 

100_8864.JPG

100_8865.JPG

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Here is a good preserved Holopea iowenis. Im surprised no one else picked it up since it was big and just sitting there on the flats. You can even see the partial furrows on it. 

100_8872.JPG

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Look like I will have to resort that group. I found one weird shaped one among what I labelled Westerna gigantea which for me usually are tighter coiled. 

100_8877 (4).jpg

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I will have to upload a different image of "westerna gigantea' that was my best speciment another time. Too large a file size even if I cropped it a lot. 

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1 hour ago, Tetradium said:

Whats #5. It look very similiar to a single cast mold that I have.

4-5 are Straparollus circinatus. I'd recommend downloading the PDF I linked above for more information as there is more than one Straparollus reported. Here's the full uncropped plate.

 

full plate.png

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