Rik's Mystery Fossils

This bone was collected on a ranch in Cochise Co. in Sept. 2000. It appears to be a shoulder or hip bone but of what creature I cannot figure out from Roemer or Carroll. Any constructive thoughts would be welcome.

This fossil is middle Cambrian. There is soft body preservation at this site so it could be non-shelly. My best guess is a colonial sponge, what's yours?

Send your guesses and suggestions to me at: rhill@lpl.arizona.edu