I wonder how bones evolve where there are none. (This is the question, read the sub-questions as examples :) )
Lets take an elephant as an example. If it was adaptive for the elephant, could bones somehow evolve in their soft-tissue trunks? If so, what tissue would they develop from?
Perhaps the sheet of cartilage in their ears are more likely to somehow calcify and become a new bone?
And would then several connected bones and joints evolve from the new bone tissue?
Is it very rare for new bones to evolve from scratch? Or, do today's bones entirely trace back to the set that evolved in early tetrapods?