I have no idea what the brown flat elongated things are in this specimen. I collected it from the lowest part of the Eagle Sandstone and upper Marias River shale. Late Cretaceous. I have found Baculites in accompanying shale. But, these are not Baculite.
The fossils in question are casts. They are composed of a fine grain umber brown material that is different than the molds. The molds are fine gray sand and clay. The casts are somewhat fragile. No apparent shell. They are long with round terminations. No suturing. A slight low ridge runs the length of each fossil. Eash fossil is about 2 1/2 to 3 inches long about 5/8 wide and about a 1/8 inch thick. These do not match the baculites I found in the accompanying shale. The baculites usually have a hard gray cast material with fine sutures. The closest possibility is belemnites but the shape seems wrong to me.
These are not bones. They lack the hallmarks of bones.