Bellerophontid from Bridgeport

[BobWill]

 

 

 

I found this in Texas, near Lake Bridgeport, in the Jasper Creek Formation, Canyon Group, Missouri Series, Pennsylvanian Sub-period.

 

The flared lip, think shell and absence of obvious sutures or septa tell me it is more likely to be a Bellerophontid gastropod than a cephalopod. The open umbilicus and the large size is making a firm ID difficult. Any ideas?

[cngodles]

Probably won’t be able to get an ID from a steinkern. Yochelson said that identification from a steinkern in this family should not be trusted as experts can’t often tell Bellerophon and Knightites apart in that state of preservation.

 

If there is any shell ornament at all, perhaps we can at least place it in a family.

[BobWill]

@cngodles I missed seeing this post from last month. Must start paying closer attention

 

I guess it was the presence of the layer seen in these close-ups that had me thinking this was a replacement fossil rather than a steinkern. I may be wrong about that but if this is shell then there is really no ornamentation to help identify it.

 

 

 

 

[BobWill]

This was finally identified as Bellerophon crassus (Meek and Worthen) which can be this large and can have ornamentation consisting only of "simple growth lines or transverse lirae."