Alright I'll stop having my fun.
A very popular theory right now is that Dracorex is basically a baby Pachycephalasaurus. Stygimolach being a juvenile.
This is supported by the spikes and bumps being in the same position throughout the stages, general anatomy being similar, and both Draco and Stygimolach having signs of being young animals.
These thoughts are going to be reflected in Saurian and in the game Prehistoric Kingdom, and maybe in others but I'm not sure.