T. Rex 'Lived Fast and Died Young'

Study Shows Rapid Growth Spurt for Monster Meat-Eater

The skull of Sue, a T. rex specimen at Chicago's Field Museum.

hide captionThe skull of "Sue," a T. rex specimen at Chicago's Field Museum.

The Field Museum
The skull of Sue, a T. rex specimen at Chicago's Field Museum.

hide captionThe skull of Sue, a T. rex specimen at Chicago's Field Museum.

The Field Museum

One of the mysteries of dinosaur evolution is how animals that started out at about three feet long grew over millions of years to become the planet's most fearsome monsters. As NPR's Christopher Joyce reports, a new study on the Tyrannosaurus rex offers some clues. It appears that in addition to being among the biggest meat-eaters ever to roam the planet, T. rex may have also been one of the fastest growing.

By studying fossilized bones from several specimens, researchers concluded that the king of dinosaurs gained five pounds a day during a four-year growth spurt in its teen years, between the ages of 14 and 18. That's a faster growth spurt than other, closely related dinosaurs studied.

The Life of T. Rex

• Roamed the Earth 65 million years ago

• Adults weighed up to 12,000 pounds

• 40 feet in length, from head to tail

• Teenage T. rex gained about 4 pound a day

• Reached adulthood at 20 years old

• Died by age 30

• 15 times larger than today's largest land carnivore, the polar bear

• Among carnivores, second only in size to the Giganotosaurus

T. rex spent about two-thirds of its life growing, reaching its adult size at about age 20. But most died around age 28. "T. rex lived fast and died young," says Gregory Erickson, study co-author and Florida State University biologist.

The scientists based their conclusions on growth rings in the ribs and other small bones from museum specimens of T. rex, such as Sue at Chicago's Field Museum.

The work, led by researchers at Florida State University, the American Museum of Natural History and the Field Museum, appears in the current issue of Nature.

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