Fossil or What?

I'm not sure if this is a fossil or the result of some sort of chemical leeching. It has the texture of the latter, but part of it looks like a shell and the strands are segemented. I wonder if it could be some sort of holdfast, that looks like a shell, for some ancient squiggly plant. I have also read that there are fossilized worm holes in the area so perhaps that is what we have. But I really have no idea. If anyone can explain this photo, please do so. The photo is from the Bear River Range of Utah. October 2009