Carboniferous Cephalopod?

[Lucid_Bot]

Found this critter in what I believe to be the Brush Creek Limestone. It is Carboniferous (Pennsylvanian), Glenshaw Formation, and looks like a nautilus to me, so I'd guess Solenochilus. Thanks for the help.

[cngodles]

Given the size and shape, Solenochilus would be a guess for me here. However, I wouldn't rule out Poterioceras. The way it tapers off into a broad tip suggests the latter, but handling the specimen would give a better idea. Ignore the fact that specimens pictured below have tightly spaced growth ornament on the shell. The camerae—like on your steinkern here—would be broad.

 

https://fossil.15656.com/catalog/specimen/CG-0500

https://fossil.15656.com/2022/06/02/poterioceras-curtum-a-breviconic-cephalopod-from-the-carboniferous/

Edited March 30, 2023 by cngodles
camerae information add.

[cngodles]

To add some more information, paleontologists considered Poterioceras to be the adult portion of Brachycycloceras. It was published as such in the Treatise of Invertebrate Paleontology. Later, new evidence and research redivided the names (Windle, 1973), prompting Niko and Mapes (2009, 2010) to redescribe species of Brachycycloceras.

 

Some websites still have the wrong name published, like the Pennsylvanian Atlas below. That is a Poterioceras, not a Brachycycloceras.

https://pennsylvanianatlas.org/species/brachycycloceras-bransoni/

Meanwhile, they have the correct type of specimen here:

https://pennsylvanianatlas.org/species/brachycycloceras-normale/

 

Taxonomists spend lots of time combining and redividing names. The lumpers and the splitters. Museums don't have the time to relabel everything in their collections.

 

[Lucid_Bot]

Is there any telling what caused those holes?

[cngodles]

Being a steinkern, what you are looking at is the empty space inside the shell that was filled with air/gasses. So if some late Pennsylvanian aged shark had bitten into the shell, it would not leave marks on the steinkern like that. The steinkern forms after the shell sinks into and is filled with sediment. I've always questioned why there are not open air chambers in these buried shells, but I've been told that being jostled and thrown around for tens of thousands of years, rock and minerals find a way in. Some recent (Dinosaur aged) ammonoids do have open air chambers when found, but I'm not sure on the why in those cases. Mapes and Mccomas (2010) did a study on septal implosion, where after death the chambers imploded and most of the walls were destroyed inwards on Metacoceras.

 

Below is what a modern shell looks like. Before burial these chambers are open. So any sort of tooth marks would be visible on the shell, but not the open spaces within.

 

But, there is always a chance. Perhaps holes on the shell disturbed the way the infill occurred, and when you separated the shell from the rock, these open cavities left a sort of mark, because they were connected from the inside to the outside. Having shell material (or the piece of the rock that was attached) would help. Either way, there is a chance.

 

MAPES, R.H. and MCCOMAS, G.A. (2010), Septal implosion in Late Carboniferous coiled nautiloids from Ohio. Lethaia, 43: 494-506.

Edited April 1, 2023 by cngodles