These are 3 pictures of what I believe to be a large vertebrae of some sort of sea creature. Im guessing that they belong to the same creature that the skull belonged to. The size comparison matches and they both appear to have been in the water for the same amount of time.

This is the closest thing to the skull that I could draw. I had another 'witness' helping me with the drawing. Note the large eye sockets, the ridge on the skull, the line of catrilage at the very end and the complete lack of teeth.