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Caleb

Proetus Trilobite From Iowa

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I collected this specimen in the Little Cedar Formation of Johnson County, IA earlier this spring, but haven't been able to find much info on trilobites from this formation. According to the University of Iowa's site Fossils in My Backyard, there are 4 Proetus species from the Devonian of Johnson County. These four are: P. arietinus, P. bumastoides, P. haldemani and P. searighti. Unfortunately the photos they have are not that great for accurately IDing this bug. I now refer to the vast knowledge base that is the F.F. and ask if anyone has knowledge of this bug or some obscure papers regarding trilobites of the Little Cedar Formation.

Proetus sp.

Little Cedar Formation

Johnson County, Iowa

Middle? Devonian

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post-3840-0-02885800-1344124342_thumb.jpg post-3840-0-37176400-1344124344_thumb.jpg post-3840-0-74815900-1344124346_thumb.jpg

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If you don't know, there's no way I would, but I had to say I can tell that's a nice one!

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This paper cited by Lieberman (1994) looks promising:

W.J. Hickerson, 1992

Trilobites from the late Givetian Solon Member, Little Cedar formation of eastern Iowa and northwestern Illinois

In:

Iowa Dept. of Natural Resources, Guidebook No. 16: J. Day and B. J. Bunker (editors)

The stratigraphy, paleontology, depositional and diagenetic history of the Middle-Upper

Devonian Cedar Valley Group of central and eastern Iowa, pp. 123-139.

Not sure if a pdf is available but the paper should be easy to discover.

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Could it be Crassiproetus instead of Proetus?

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Could it be Crassiproetus instead of Proetus?

It very likely could, In the paper "Geologic Reconnaissance of the Corralville Lake Area" Orrin Plocher, 1989 they are all listed as Crassiproetus.

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Looks like the taxonomy has gotten tangled over the years. Plenty of references lumping these together as Proetus (Crassiproetus). One interesting paper is actually titled: Proetida - a disorderly order of trilobites :o:P I'm finding numerous examples of each that are similar to your trilobite. You should email Bruce Lieberman to find out the current status on the Little Cedar proetids.

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Here is one of Hickerson's illustrations of Crassiproetus occidens from the lower Rapid Member from the Quad Cities. This is from the Geological Society of Iowa Guidebook No. 59, Paleozoic Stratigraphy of the Quad-Cities Region:

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I have this piece of a proetid from Johnson county. The bump on the top of the head is a drop of water, I was trying to bring out some of the detail by wetting it. Somewhere I have a paper by Hickerson where he identifies several species by the pattern of the dark furrows on the head. I think I misplaced the paper.

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Lieberman also mentions a few of the Little Cedar proetid species (bumastoides, searighti) as: Crassiproetus. The website Caleb referenced credits the University of Iowa with these IDs. I'm wondering if this is a careless oversight by a grad student or if Jonathan Adrain was actually consulted in the process when the photos were assembled?

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After reading through the descriptions and comparing my specimen, I think I may have landed on a possible ID. However, this possible ID cannot be certain according to the description comments. Oh the fun! The line drawing is not the greatest, and decent photos have proved difficult to find, but I think it may be Crassiproetus cf. arietinus (Walter, 1923). I have noted features that comply with the description and line drawing.

Description

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Line Drawing

post-3840-0-03167900-1344259132_thumb.jpg

Edited Photo

post-3840-0-74815100-1344259127_thumb.jpg

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