The whale skeleton I keep trying to prepare

I'm in the prep lab and the whale skeleton is still half-encased in matrix, but the bones keep changing—ribs become vertebrae, the skull turns into a fish skeleton, then back again. I keep chipping away but the jackhammer in my hand is a toothbrush. I wake up annoyed, like I'd almost gotten it clean. I've been a paleontologist long enough to know this is just my brain chewing on something, but the frustration feels real.