Thread:TheSquidychicken/@comment-31308946-20170525193032/@comment-26335978-20170702034408

Finding a fossil with real bones is very rare with old fossils. The reason they are still visible is either because they have been preserved somewhere where bacteria cannot access them, so they don't decompose, or more commonly because from permineralization. That happens because minerals fill the cellular spaces and crystallize, slowly replacing the original plant or animal.