Boy Dons Thinking Cap

Some recent conversation follows. (See how long it takes to establish which quotes are "mother" and which are "son." Or, and please don't correct me where I'm all wrong about fossil formation...)

"Fossils are HUGE things -- GIGANTIC!"
"Well, not all fossils are big. If you start with a small animal, you'll end up with a small fossil, because a fossil is like a picture of the animal's bones, just the size they were when the animal died."
After a brief pause: "OOOHH! So, like, if a chicken dies, we will find little bones... LOTS of little ones."

Then, the next day:
"If a squirrel dies, we will find medium bones. But if a tree falls over and dies, we won't find ANY bones, because trees don't even HAVE bones!"
"That's right. They have bark that's hard like our skeletons, and it helps hold them up."
"Yeah, Mom, that is why it's called the skin of the tree."