This doesn't change the argument that the foreheads are scales, though. You will have to show me an occurrence in nature where skin is so thin that it follows the contours of the underlying bone structure so completely it descends into grooves as well as rising up onto the ridges in perfect detail.
Make a fist. Look at your knuckles.
Besides, it's canonical that the ridges are part of the bone structure. Here's a prop Klingon skull used in ENT:
http://brblife.wordpress.com/2008/04/30/star-trek-ent-“klingon-skull”-for-auction/