Domatoceras Perhaps?

[cngodles]

So most of what I find is Metacoceras or Pseudorthoceras, two very common cephalopods locally. I've found a few Solenochilus, but they are different enough that I know what I found right away.

 

This specimen was discovered as a body chamber. I thought Metacoceras, because, why not? Anything of this shape usually is. After some moderate prep, I revealed some more body chamber, but not any suture marks. The venter is oddly shaped as well, with a shallow U shape. It might be crushed, so I didn't pay it too much mind. I also discovered that the body chamber is much larger than any Metacoceras specimen I have found to date.

 

In viewing the paper A NAUTILOID CEPHALOPOD FAUNA FROM THE PENNSYLVANIAN WINTERSET LIMESTONE OF JACKSON COUNTY, MISSOURI (full paper), I found plate 5 which features Domatoceras. They are known to exist here, but I've never found anything definitive. Here is the plate from the article:

 

 

Here is a Metacoceras (CG-0071) on the left, and the specimen in question (CG-0068) on the right.

 

 

Here is the venter of CG-0068 showing the two ridges marked with arrows. I feel these are similar to the ridges shown in Figure 2 of Plate 5

 

 

And that is that. Any cephalopod people have an opinion? I could prep it more, it's just at the labor intensive micro prepping state right now with solid cement like limestone overlaying it.

 

One more photo of it for some additional context:

 

 

 

 

 

[cngodles]

I got one opinion that this is likely a Domatoceras, so I'm calling off the search.