Actually, I've been thinking. In season one, there were two different versions of regular Dragonoid, right? Drago, and the ones Drago had to face in his battle agianst Apollonir. Apollonir's Dragonoids had no horns. Maybe the horn signifies Drago's important-ness. So those Hyper Dragonoids didn't have horns because they aren't important Dragonoids. But since Dan's is, that means if he evolves into Hyper Dragonoid, he will have horns. Just my thought.