instead of one big one on his back how about 2 of these mounted to his flanks and a guy ontop to reload them:

http://www.frapanthers.com/teachers/white/galleries/roman_artillary/Ballista.jpg 

take away the stand and they would sit flat against his side. - kinda like a harness with these instead of stirrups

Exxcentric unfortunately it has to be a catapult cause it's used for long range indirect fire like artillery. I'm not above adding extra Balistas but I'd rather not replace them as his main ability is integral to indirect fire.

CosMoe unfortunately the only design constraints are dinosaur and Turnbuckle so he can't throw with his tail. He doesn't need to be a T-Rex. A Stegadon might work but I can't put more then one person on the things back with out running out of polygons.

A friend did a couple silhouettes. It does seem possible to keep the catapult. I actually really like the Brachiosaurus but I'm not sure how he would attack normally.

It's in reference to FrogBoy's comment

Demigod 2:  Dinasaur like creature (General) Projectile Catapult Evil.

Power 1: Long range trebuchet type power. (Kind of like Regulus but it strikes an area for an area effect)

Power 2: Tail slam, short range area effect on towers or units alike.

Power 3: Flag lock for 10s, 20s, 30s, 50s

Power 4: Stun (slams its tail down on the ground causing nearby units to be momentarily stunned - 1s, 2s, 3s, 4s.

Skill tree path: Spikes: Causes attacking units to take increasing amounts of rebound damage.

Skill tree path: Enhanced HP (gets extra HP)

Triceratops looks best !

1. Triceratops

2. T-Rex

3. Brachiosaurus

4. whatever

lol poly shut up, its a kool idea. Those catipultisari are anti-building, and these things would be aoe guys. They could be desinged to devastate mobs.