Unknown orthocone

[fossilzz]

So I have partially removed an orthocone from a nodule that I found in some eroded glacial till. The rock is most likely silurian in age but I can't don't recognize this orthocone. It seems to have faint striations running lengthwise down the shell, which I haven't seen before.

[Fossildude19]

Can we see pictures of the ends? 

[fossilzz]

The ends are worn flat because they are in a nodule, and I didn't see a siphuncle, however the nodule cracked in half so here is a cross section.

[FossilDAWG]

To ID such cephalopods with confidence, one needs to see the structure and location of the siphuncle, as well as the shape of the camerae (chambers) and the nature of any cameral deposits. Even if those features are not exposed, you can often make an "educated guess" if you know the source formation and can access publications on the known fauna of that formation.  In this case we don't have a source formation, and the specimen is dolomitized such that the position and shape of the siphuncle is obscure.  All I can suggest is that the ornament (longitudinal striations, without ribs) and spacing of the suture lines suggests Kionoceras as a possible genus, assumig the fossil is Silurian or possibly Ordovician.

 

Don

[fossilzz]

Thanks for suggesting Kionoceras, I searched that up and found a similar specimen from the Lockport Dolostone, which is a local formation for me and is quite possibly where this specimen came from. I think your right that I won't be able to confidently narrow this down to a species, as the nodule was cracked open when I found it and the fossil is quite worn.