From around age 14 to 18, T. rex took on about 70 percent of its adult mass, growing from a 1-ton carnivorous lizard to a bone-crushing, 6-ton dinosaur eating machine with few rivals in the prehistoric kingdom, according to FSU biologist Gregory Erickson. At the peak of this spurt, T. rex grew more than 4.5 pounds a day.

Erickson and his team of paleontologists are the first to establish an accurate picture of how T. rex accelerated its growth over a relatively few years to become gargantuan while earlier, smaller relatives had much slower growth. The scientists did this by counting growth rings in the bones of T. rex and other members of its family and calculating the corresponding body size by measuring the circumference of the femur.

The research is featured as the cover story for the Aug. 12 edition of the journal Nature.

T. rex's growth rate is comparable to that of the modern day elephant. But while elephants have a lifespan of more than 70 years, T. rex lived no more than 30 years.

"We now know that T. rex lived fast and died young," said Erickson.

Erickson and Peter Makovicky, dinosaur curator at The Field Museum and a coauthor of the study, will join with other team members at the Chicago museum on Wednesday to announce their findings. The museum is home to Sue [The Field Museum], the world's largest, oldest and most complete T. rex fossil, which was discovered in South Dakota in 1990.

Erickson has spent much of his career exploring how some dinosaurs got so big. The first dinosaurs to roam the Earth some 225 million years ago were about a yard long and weighed between 50 to 100 pounds, he said. The giants, such
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Contact: Gregory Erickson
gerickson@bio.fsu.edu
850-645-4991
Florida State University
11-Aug-2004