October 14, 2011
CHICAGO (AFP) - The iconic T. rex dinosaur grew bigger and faster than previously estimated, according to new methods based on actual skeletons instead of scale models, British and US scientists said Wednesday.
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.
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.
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.
"We knew she was big but the 30 percent increase in her weight was unexpected," said Makovicky.
The technique used mounted skeletons to derive body mass estimates, instead of models created to scale.
The team made three-dimensional laser scans of the skeletons to form a template for digital models that would add simulated flesh.
They devised three different levels of the approximate amount of flesh the creatures likely had, to figure the size of a thin, hungry animal up to a well-fed one.
"Previous methods for calculating mass relied on scale models, which can magnify even minor errors, or on extrapolations from living animals with very different body plans from dinosaurs," said Makovicky.
"We overcame such problems by using the actual skeletons as a starting point for our study."
By establishing new sizes for the other four specimens studied, the researchers also found that the creatures likely grew faster than initially thought.
"We estimate they grew as fast as 3,950 pounds (1,790 kilograms) per year during the teenage period of growth, which is more than twice the previous estimate," said lead author Hutchinson.
That would mean the land-roaming carnivores expanded by about 11 pounds (five kilograms) per day during their peak growth spurt.
The same team had estimated in 2004 that T. rex gained 4.6 pounds (2.1 kilograms) per day.
