- The Washington Times - Thursday, August 12, 2004

NEW YORK (AP) — Think your teenager is growing fast? A new study says Tyrannosaurus rex launched into an explosive growth spurt in its teen years, packing on an average of nearly 5 pounds a day.

That spurt, from ages 14 to 18, let T. rex pick up most of its eventual adult weight of about 6 tons, the research says. It stopped growing around age 20 and apparently died by age 30, researchers estimated.

T. rex was “the James Dean of dinosaurs — it lived fast and died young,” said Gregory Erickson of Florida State University, one of the scientists presenting a study of the reptile’s growth pattern in today’s issue of the journal Nature.

In contrast, he said, although an African elephant’s growth reaches a plateau at around the same age and weight, that animal lives past age 50.

Scientists have long wondered how the huge dinosaurs got so big. Did they grow slowly for a long time, or very quickly for a shorter period? Or was it a combination? The question must be studied separately for various kinds of dinosaurs, experts said.

T. rex was one of the largest meat-eaters ever to walk the land when it died out about 65 million years ago. At an elephantlike 6 tons, it stretched about 45 feet long and measured about 13 feet tall at the hip. The adult skull alone was 5 feet long, with teeth up to a foot long.

“T. rex is one of the dinosaurs that could eat a human being in probably two bites,” said Thomas Holtz Jr. of the University of Maryland. “One bite would take off the top, and the next bite would take off the hips and legs.”

Mr. Holtz, who didn’t participate in the study, called it important and said it could help answer other questions about T. rex. For example, he said, it looks as if the creature got so big after age 12 that it might not have been able to run as fast as before. So maybe it stopped running after prey and turned more to either scavenging or ambushing its meals, he said.

The research is consistent with the hypothesis that younger T. rexes often separated a victim from its herd so “the big bruiser parent could take it down,” Mr. Holtz said.

It’s not surprising that T. rex showed explosive growth in adolescence, because that pattern had been detected in other kinds of dinosaurs, Mr. Holtz said. But the estimated lifetime of a T. rex is surprisingly brief — its mammal-like rapid growth wasn’t followed by a mammal-like longevity, he said.

Mr. Erickson agreed that the growth-pattern work opens the door to studying many other things about T. rexes, although he said it doesn’t settle the old question of whether it was primarily a predator or a scavenger.

Mr. Erickson and colleagues established the growth pattern by analyzing more than 60 bones from 20 specimens of T. rex and three of its smaller evolutionary cousins. They deduced the animals’ ages at death — which ranged from 2 to 28 years — by studying growth lines, somewhat like counting the rings in a tree trunk. They estimated the animals’ weights from the circumference of the thigh bone.

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