Countertop Drawing

I walked into the bird prep lab of the Field Museum last week and saw this pencil drawing on one of the countertops. After asking around a bit for the drawing's creator, I was told it was by Tom Gnoske, assistant bird collections manager, as he had been in the night before working in the lab. I'm not sure how this came about, but it's an impressive rendering by someone that has an intimate knowledge of mammal anatomy.