 The skull was perched at the end of a thick , S @-@ shaped neck , and a long , heavy tail acted as a counterweight to balance out the head and torso , with the center of mass over the hips . Tyrannosaurids are known for their proportionately very small two @-@ fingered forelimbs , although remnants of a vestigial third digit are sometimes found . Tarbosaurus had the shortest forelimbs compared to its body size , while Daspletosaurus had the longest . 
