Trap it with 2 Dino gates and a behemoth gate and door and use fence foundations (all stone) to help you make a triangular shape for the trap. Then have it chase you into the trap and close the behemoth gate and knock out with a paracer w/ a catapult on one side of the platform saddle
Tranq Arrows/Darts DO NOT WORK!!! To knock this out you need to use a catapult and shoot in only on it's back. If you shoot it on it's legs it will kill it. UP-VOTE SO EVERYONE KNOWS & TO GET DODODEX TO ADD THIS!!!