At that size, Raye's bite should be like a pinprick. But Raye is not a normal human being, and the bite actually causes the rex to roar in pain, releasing Raye and rolling to the side in a sort of twitch reaction.

You ever see a flightless bird attempting to get up off that ground? Because that's what the Rex is doing as it attempts to scramble back to its feet before Raye can.