Middle Pennsylvanian Nautiloid?

[Titan]

I recently got to do some hunting in northern Missouri, Marmaton group and found a few large phosphatic concretions. Within one was this specimen that I am trying to identify. I am wondering if it looks like a Solenochilus sp. to anyone beside me?

 

 

 

 

There may not be enough of the specimen present to determine a species ID, but I figured I'd take a shot for the sake of labeling.

 

Thanks,

[connorp]

@cngodles

[Fossildude19]

The ornamentation on this look more gastropod-ish to me.    

 

@Missourian

[cngodles]

It has the Solenochilus shape but is a bit flat looking. Any plans on cleaning it up? The bit here looks interesting.

[Titan]

@cngodlesIII don't have the option to prep it out at all presently. In the future hopefully but I'm not sure when. Thanks for your input I appreciate it! I'll leave it as an unknown for now.

[cngodles]

Another to consider is Domatoceras. I’ve found I think two of them, but both are not a sure ID. They are usually a tall thin shell shape. Your shell appears thin and has the same inside curve.

[fifbrindacier]

Hi everybody. 

Firstly i also thought the ornementations were from a gastropod, but now I think a solenochilus is a good candidate. 

https://link.springer.com/article/10.1134/S003103011814006X/figures/1

[Titan]

@cngodles thanks for the additional species to consider.

 

@fifbrindacier Thank you for that link! I had seen a few similar pictures that I was basing my identification on.

[cngodles]

One last observation is that it appears to be lying on it's side. Nearly every one I have found so far has been sitting in an almost up-right position. This is due to the end body chamber typically being so much wider than the rest of the shell, and the shells being very round. These rapidly expanding conchs do so very quickly. From end-to-end of the body chamber is often the largest, straightest part of the shell and offers the most likely resting position.

 

With the rapidly expanding conch, I don't believe you easily get an inside circle shape that large.

 

This is my write-up on one that I found almost lying on it's side: https://fossil.15656.com/2020/04/24/solenochilus-iv/

[Titan]

@cngodles That is very interesting and I will take your word for it. Awesome website as well. You've put a lot of work into it and it shows!

 

One thing that seems of interest to me is that it's from a circular disk shaped phosphate concretion roughly 1.5 ft wide by 1 ft high that was filled with other shells (brachiopods and gastropods) as well as a small fin. I didn't have the tools necessary to get into the center of it, but the outer layers had many different specimens present. I plan to go back with the right tools as soon as I can as there were many other concretions I wasn't able to open. I am really regretting not having the ability to prep it out as that might help narrow down the ID.

 

Do you think it may be a gastropod of some kind?

 

[Titan]

All that to say that I wonder if there couldn't be some decomposition involved though that still doesn't explain the size of the inside circle.

[cngodles]

I asked my friend (who’s favorite subject is Paleozoic gastropods) if there was a general largest width for known Carboniferous Gastropods, and he isn’t sure. He did mention that ones from Texas tend to be larger than ones up here in Pennsylvania.

 

I generally see cephalopod in your photos above much more than gastropod.

[Titan]

Cool, maybe it'll become more apparent after I get to prep it out. It's actually from northern Missouri, up near Iowa. Thanks for your feedback!