From Andrew Evans, Cosheston, Pembrokeshire, UK
Aren’t T. rex’s small arms a question of balance? A bipedal theropod would have balanced over its hip joints. If its skull was enlarging due to evolutionary pressure, as described, then this increased mass would be counterbalanced by a heavier or longer tail. The evolution of lighter arms would keep the increasing weight of its front half to a minimum. Arms would still be very useful but the optimal size smaller (30 May, p 17).
