 The tyrannosaurids were all large animals , with all species capable of weighing at least 1 metric ton . A single specimen of Alioramus of an individual estimated at between 5 and 6 metres ( 16 and 20 ft ) long has been discovered , although it is considered by some experts to be a juvenile . Albertosaurus , Gorgosaurus and Daspletosaurus all measured between 8 and 10 metres ( 26 and 33 ft ) long , while Tarbosaurus reached lengths of 12 metres ( 39 ft ) from snout to tail . The massive Tyrannosaurus reached 12 @.@ 3 metres ( 40 ft ) in the largest specimen , FMNH PR2081 . 
