So it can make the complete mini-T-Rex mode without the headmaster?

I was looking at the pictures before, and it looks a lot like the headmaster guy makes the arms and lower jaw of the dinosaur to me.
Hope I'm wrong, 'cos I really like the look of the little dino-bird-thing, especially his dino-mode, so it'd suck to have to choose between keeping Skullcruncher in crocodile mode VS not being able to complete the dino-dude.