St. Leon Mystery

[Tidgy's Dad]

Hello, once again, my friends.

Another puzzle from the Southgate Hill road cutting near St. Leon, Indiana. It will be Cincinnatian, Late Ordovician in age from the Waynesville or Liberty or Formations. The rock it is in also contains Strophomena planumbona, Eochonetes clarksvillensis, Zygospira modesta and Bythopora deliculata. 

The shape and growth lines seem to me like the inarticulate brachiopod Pseudolingula, but the 'ribs' and 'tubercles' wouldn't fir this. Looking more closely it seems to have a bryozoan structure, so is it a brachiopod covered in an encrusting bryozoan? Or just a weird bryozoan? 

My other thought is some sort of trilobit, a hypostome, maybe? Also bryozoan covered?

Any of your opinions will be gratefully received.

Thank you

It is 4 mm wide. 

Here it is with a tiny Zygospira modesta :

And as close as I can get :

Each 'level' gets progressively higher but the total height of the specimen can't be much more than a mm. 

[Al Dente]

Maybe something similar to Petrocrania?

[Tidgy's Dad]

1 hour ago, Al Dente said:

Maybe something similar to Petrocrania?

Interesting thought and one I hadn't considered. 

Petrocrania scabiosa does occur in these formations, usually encrusting Rafinesquina. 

This specimen could have been encrusting another type of brachiopod, maybe an orthid with thicker ribs, and then the piece has broken off and been preserved free of the rest of the host brachiopod. 

It's at least a possibility.

Thank you.