Pennsylvanian Mystery Plant

[historianmichael]

After searching through a couple of publications on Pennsylvanian plants, I am a bit stumped on what this plant could be. It is certainly not the classic fern or horsetail that one often collects from the Llewellyn Formation of Eastern Pennsylvania. The preservation is ok - not perfect, but better than some plant material I have collected from this site. I unfortunately broke the piece trying to transport it out of the site. 

 

 

Here is an attempted close-up of the individual leaves and their venation

 

Here is the negative with some more preserved venation

 

Any help is greatly appreciated. Thank you!