Indiana Trace Fossils

[Edward Engelbrecht]

Years ago I picked up these fossils in southern Indiana. I began looking them over again recently. I'll explain what I understand about them. 

Matrix: Ironstone concretions

Classified: Carboniferous?

Location: Millsport, Jackson County, IN; Muscatatuck River bed

 

I found these fossils below the Rte. 135 bridge over the Muscatatuck River, which runs at the base of a large hill south of the river. As I recall, the rockface of the hill is gray shale. I believe the concretions are washing out of the shale and tumbling into the river. The river runs on or near the ends of glacier worn plains. The glaciers less affected the hilly region to the south. Here is the fossil trace that has always confused me:

 

In the same matrix occurs the following bivalves of various sizes:

 

 

I've added three pictures of the large bivalve because it is unusually tall compared to most bivalves I've seen. There are fine ribs running from the dorsal to the ventral ends. The concentric ribs are like large wrinkles. Within the concretion that held the large bivalve, I found mirror images of a flattened tube shape. The mirrored look reminds me of plant fossils in Carboniferous rock closer to Terre Haute, IN. I'm grateful for any suggestions or references. Thank you.

[Tidgy's Dad]

Photos 2,3 and 4 would seem to be a productid brachiopod, not a bivalve. 

[Edward Engelbrecht]

Thank you, Tidgy's Dad, for your suggestion. I'm learning more about brachiopods to see whether that helps. I'm also going to try to remove more of the matrix to see whether that reveals any more clues. One thing I note from reading is that the productid often have spines on their shells. And this creature does not have spines.

Edited April 4, 2022 by Edward Engelbrecht