Can you help identify this cephalopod?

[Eastonian]

Hi, all. I collected this specimen in the New Point Stone quarry, near Napoleon, Ind. It's Silurian, and was found in the Massie Shale. But I can't seem to find any information about it, specifically, the genus or species. The experts to whom I reached out were stumped. Any ideas, ladies and gentlemen?

[Mark Kmiecik]

I don't see a siphuncle. Could it be a really weathered crinoid columnal fragment?

[Ludwigia]

I was wondering the same thing.

[Tidgy's Dad]

Could we see photos of both ends, please? 

[BobWill]

3 hours ago, Mark Kmiecik said:

I don't see a siphuncle. Could it be a really weathered crinoid columnal fragment?

 

2 hours ago, Ludwigia said:

I was wondering the same thing.

Would we see a siphuncle from a side view? I discounted crinoid because of the slight taper. There are plenty of Silurian candidates among the actinocerids and orthocerids. Maybe someone who collects there will know what you should expect to find.

[Eastonian]

Unfortunately, these photos of both ends will probably be inconclusive. Also, to the question of whether this could be a crinoid columnal, in a third photo I've included the specimen plus a columnal found on the same site on the same day. I see the similarities. However, the segments on the specimen seem to overlap, vs. the stacked disks on a columnal. 

[BobWill]

Yes, you can see the rounded margins on the septa and get sense of the overlapping cameral deposits.

[FossilDAWG]

Looks like a nautiloid to me.  The taper, the slight curve to the septa, and the lack of crenulations (which you would expect to see where crinoid stem segments meet) all indicate an orthoconic nautiloid.

 

Don