Tyrannosaurus rex, that coolest of all the dinosaurs, may have been even bigger and scarier than originally thought. That's the conclusion that was recently reached by a team of scientists, who used computer modeling technology to estimate the average body mass of the carnivorous dinosaurs. After digitally "fleshing out" existing T. rex skeletons, the researchers now believe that the reptiles grew twice as fast, and reached adult weights up to 30 percent higher than previously assumed.

The research was conducted by scientists at The Royal Veterinary College, in London, and The Field Museum of Natural History, in Chicago.

Previous attempts at estimating dinosaur body mass have used either scaled-down models, or extrapolations based on living animals that don't necessarily have the same body layout as dinosaurs. This study, however, used five actual T. rex skeletons as the starting point.

These skeletons were laser-scanned, to produce 3D computer models. Using the relationships of the soft tissues to skeletons in birds and crocodiles as a guide, digital body cross-sections were then created along the length of each skeleton, with a virtual skin overlaid on each one. The mass of each section was then calculated, with empty spaces such as the lungs and mouth cavity not being included in the final figures.

Just as there is no one standard size for homo sapiens, however, there was likely also a considerable variety of body sizes for T. rex. To allow for that margin of error, each body section on each skeleton was modeled at three conceivable levels of fleshiness. In this way, the scientists were left with a general but more meaningful range of sizes, as opposed to one middle-of-the-road size that most tyrannosaurs probably either overshot or never reached.

The results of the study indicate that teenage T. rexes grew as fast as 3,950 pounds (1,790 kg) a year, which is double what was previously believed. One of the large adult skeletons, which resides at the Field Museum and is known as SUE, is now thought to have come from a dinosaur that weighed approximately nine tons (8.16 tonnes) - a 30 percent increase over the former estimate.

Interestingly, however, the models also suggested that the juvenile dinosaur represented by the smallest of the skeletons was probably lighter than previously thought. Additionally, based on muscle modeling of the legs of all five skeletons, the study backs up the existing assumption that large tyrannosaurs slowed down as they grew up, with large adults only managing a top running speed of around 10-25 mph, or 17-40 km/h.