Fig. 6. Hypothesized running postures of a juvenile Allosaurus. (A) A horizontal posture of trunk and tail may have been appropriate for prey capture but would have unnecessarily increased the rotational inertia during running. (B) To increase turning performance, theropod dinosaurs may have run with their trunk and tail arched in a jack-knife posture, their neck may have been sharply arched backwards to hold the head closer to the hindlimbs and they may have held their arms backwards along the sides of the body. The angle of the jack-knife posture would not have to have been as dramatic as illustrated in B to reduce rotational inertia significantly.
