So this was the largest bone we picked up on our great Out West trip. We had found it out on a ranch in Montana, as part of the Hell Creek formation. The bulk of the bone was a bit fragmentary, so our guide put a plaster wrap over the top of it. Turns out she just applied it directly to the bone, so I've spent the past few days scraping and scrubbing to get the plaster off.  I reglued the loose pieces as they came off, and assembled the fragments that were directly around the bone (during excava