Mississippian horseshoe crab trace fossil?

[Crinoids]

I had a trip out to the Buffalo wallow group in KY a few years back and found this. I am curious if it is some sort of telson drag mark. 

 

The center mark as well looks like a possible trace fossil but could be geologic. 

 

 

[Rockwood]

The center of the bryozoan Archimedes is my thought.

[westcoast]

I don't know what this is, it could possibly be a telson drag mark but it doesn't quite look right,  but it is not a horseshoe crab trace fossil (search for Kouphichnium for examples)

[Carl]

Convinced this is not a limulid trace. But it is very interesting. Beyond that, I'm a bit stumped. Could be a plant body fossil, could be an invertebrate trace.