Wikipedia: Fish scales are dermally derived, specifically in the mesoderm. This fact distinguishes them from reptile scales paleontologically. So aren't reptilia scales also dermally derived?
Based on pictures, it seems to me that a vast majority of fish species that have scales do NOT have scales on their heads. Is that fact true? To make this properly answerable: lets' define a ...
What is the evolution of hairs? Did they evolve from scales?
Were they developed anew or a heritage from fish?