The premise of them all being generally similar keratinous/chitinous extrusions with common comparative biological origins (referencing embryonic development as

The premise of them all being generally similar keratinous/chitinous extrusions with common comparative biological origins (referencing embryonic development as the hint that they all stemmed from the same root origins), has been taught in high school biology for a long time now. I remember learning that in the 1990's. I guess it bares repeating, and anyway, now we (the royal we) also have the genetic component mapped.