I also bought a skull home to look at. I wasn't intending to do this straight after work but he was very excited and asked if we could do it now. So I couldn't resist.
Basically he draw loads of lines and a few circles.
I love the end result. We have had several family requests for one of their own.
We counted bones as he was looking at the Skeleton to copy it as well as naming the bones ( preschool level).
Sarah and Dylan 3.6 months