Tyrannosaurus rex could have been even bigger than previously thought, new research suggests.

Scientists now believe the dinosaur could have been 70% heavier and 25% longer.

The largest of the species may have weighed roughly 15 tonnes instead of 8.8 and measured 15 meters instead of 12.

Dr. Jordan Mallon, of the Canadian Museum of Nature in Ottawa, said scientists "really have no idea from the fossil record about the absolute sizes they might have reached".

"It's fun to think about a 15-tonne T. rex, but the implications are also interesting from a biomechanical or ecological perspective," he added.

The study, conducted by Dr. Mallon and Dr. David Hone of Queen Mary University of London, used computer modeling to assess a population of T. rex based on living alligators, which were chosen for their large size and close kinship with the dinosaurs

Taking into consideration factors such as population size, growth rate, lifespan, and the incompleteness of fossil records, researchers said their findings suggest there must have been larger dinosaurs out there that have not yet been found.

They said the largest known T. rex fossils probably fall in the 99th percentile, representing the top 1% of body size, but bigger could still be found.

Dr Hone said: "Some isolated bones and pieces certainly hint at still larger individuals than for which we currently have skeletons."

However, to find an animal in the top 99.99% of body size, researchers think they would have to excavate fossils at the current rate for another 1,000 years.

The findings were published in the journal Ecology and Evolution.