The iconic Tyrannosaurus Rex grew faster and weighed more than previously thought, suggesting the fearsome predator would have been a ravenous teenager, researchers said Wednesday.

British and US scientists digitally modeled flesh on five mounted T-Rex skeletons and showed that the meat-eating lizard kings were up to a third bigger and grew two times as fast into adults than previous research had suggested.

One of the skeletons included in the study was “Sue,” the largest and most complete T-Rex specimen ever found, on display at The Field Museum.

The 67-million-year-old dino was discovered in 1990 on an Indian reservation in South Dakota by American paleontologist Sue Hendrickson. Named after its finder, “Sue” was previously thought to be about the size of a big elephant or rhinoceros, standing 12 feet high (3.5 meters) and 42 feet (13 meters) from head to tail.

Her living weight was guessed to be 14,000 pounds (6,400 kilograms), or about six tons. But the latest methods found she would have tipped the scales at well over nine tons.

By establishing new sizes for the other four specimens studied, the researchers also found that the creatures likely grew faster than initially thought.

They estimate that they grew as fast as 3,950 pounds (1,790 kilograms) per year during the adolescent period of growth, which is more than twice the previous estimate. That a whole lot of duck-billed dinosaurs they needed to be chowing down on. Hadrosaurs or duck-billed dinosaurs were common plant-eaters that lived alongside T-Rex, making them an obvious meal for the giant meat-eaters.

A huge appetite means T-Rex would have needed extensive territory and they were probably relatively rare. Their rapid teenage growth spurt also suggests they must have had a high metabolic rate, fuelling the idea they were warm-blooded.

The findings, led by John Hutchinson of The Royal Veterinary College, London, and Peter Makovicky, curator of dinosaurs at The Field Museum of Natural History in Chicago, are published in the journal PloS One.