There is UCMP 118742. A single bone (a tooth-bearing maxilla), it is not known for certain if it is in fact _T. rex_, but it is 29% longer than the equivalent bone from AMNH 5027 (in case you're not up on the specimen numbers, 5027 is the skeleton most people think of when they think of predatory dinosaurs -- the display specimen in the American Museum of Natural History's Hall of Saurischian Dinosaurs, formerly in the Hall of Late Dinosaurs in a more artificial pose, which is how most people probably remember it). Gregory Paul estimated in 1988 that 118742, in life, may have been 12 tonnes in mass and 13,6 m (about 45 ft) long. He also guesses that if 118742 is indeed _Tyrannosaurus rex_, then all the other known big specimens may just be subadults, and it may have been fairly common for _T. rex_ to get up to 15 tonnes, with an occasional 20-tonne behemoth that would probably have been too rare for us to ever find a fossil of it.
-- --Sean http://www.livejournal.com/users/spclsd223/