I actually agree Breludicolo. I was concerned about that when I did the initial line art-- but I was too lazy to fix it, and it's not all that noticeable. In any case, this is use proportions, and the size of the head was meant to be exhagerated to get that "movement"-- I just exhagerated a bit too much. :P
For instance, Tyranitar's hand in my avatar is also too big (compared to the official art, and to the background arm). That doesn't matter too much though, because sometimes feeling/perception/impression of the piece is more important that exactness-- especially of anatomy of fictional creatures.