New information on the skull of the enigmatic theropod Spinosaurus, with remarks on its size and affinities. 2005. C. Dal Sasso, et al. Journal of Vertebrate Paleontology 25: 888-896
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From the London Telegraph comes this report:
Newly obtained remains of Spinosaurus suggest it stretched about 56ft from nose to tail and weighed about eight tons, dwarfing its closest rival meat-eaters.
The vicious behemoth preyed among the swamps, bogs and muddy river banks of the Sahara during the Cretaceous Period - about 100 million years ago. Unusually for a large predator, fossil evidence suggests most of its diet consisted of fish.
Analysis of skull fragments suggest that when Spinosaurus squared up to T.rex in the 2001 film Jurassic Park III, its gigantic proportions were under-estimated. Dr Paul Barratt, a dinosaur researcher at the Natural History Museum, said: "These measurements would make Spinosaurus considerably larger than T rex and the largest land-based predator ever to have lived."
Cristiano Dal Sasso and colleagues of the Civic Natural History Musuem in Milan, Italy, have carried out an examination of a spinosaur snout measuring 3ft 3in that was unearthed in Morocco. They also analysed previously unidentified bones from the upper rear of the skull. From these the researchers calculated that the skull was 5ft 9in long.
Note: Without having read the paper I'd suggest that extrapolating total body length (or even skull length) based on a few skull fragments is problematic at best.