 Tyrannosaurus was acknowledged by Spielberg as " the star of the movie " , even leading him to rewrite the ending to feature the T. rex for fear of disappointing the audience . Winston 's animatronic T. rex stood 20 feet ( 6 @.@ 1 m ) , weighed 17 @,@ 500 pounds ( 7 @,@ 900 kg ) , and was 40 feet ( 12 m ) long . Jack Horner called it " the closest I 've ever been to a live dinosaur " . While the consulting paleontologists did not have a consensus on the dinosaur 's movement , particularly regarding its running capabilities , animator Steve Williams decided to " throw physics out the window and create a T. rex that moved at sixty miles per hour even though its hollow bones would have busted if it ran that fast " . The major reason was the T. rex chasing a Jeep , a scene that took two months to finish . The dinosaur is depicted with a vision system based on movement , though later studies indicated the T. rex had binocular vision comparable to a bird of prey . Its roar is a baby elephant mixed with a tiger and an alligator , and its breath is a whale 's blow . A dog attacking a rope toy was used for the sounds of the T. rex tearing a Gallimimus apart , while cut sequoias crashing to the ground became the sound of the dinosaur 's footsteps . 
