(CNN)Researchers have long known that the meat-eating Tyrannosaurus rex had a teenage growth spurt, gaining around 35 to 45 pounds per week, to reach its colossal size.
But up until now, it hasn't been clear whether all dinosaurs shared this growth pattern. Was a T. rex-style period of extreme growth the only way dinos became full-fledged adults?
A study of fossilized bone samples from 11 different dinosaurs published Tuesday has revealed that while some transformed during an adolescent growth spurt, others grew slow and steady.
Like tree trunks, dinosaur bones have rings that show how the creatures grew and aged.
"Most animals have a period every year when they stop growing, traditionally suggested to be in times like winter when food is more scarce. It shows up in the bones as a line, like a tree ring," said Tom Cullen, a scientific affiliate of Chicago's Field Museum and the lead author of a new study in Proceedings of the Royal Society B.
"By analyzing these growth lines and examining the bones for new regions of growth, scientists can get a rough estimate of an animal's age and how much it grew every year. There are also clues in the bone structure," he said in a news statement.
The dinosaurs' growth patterns depended on their family, the researchers found. T. rex and its relatives, the coelurosaurs, showed a period of fast growth during adolescence, and then the rate of growth would peter out once they reached adulthood.
However, more distant cousins of the T. rex, the research suggested, could reach a similar size but grew more slowly.
The team sampled bones from a Carcharodontosaurus, a newly identified species from Argentina. It didn't reach its adult size until its 30s and 40s and lived to be up to 50 years old or more. Despite its advanced age, it had only stopped growing two or three years before becoming part of the fossil record.
For the study, Cullen also took a sample from the Field Museum's most famous resident dinosaur, Sue the T. rex. It lived to be about 33 years old and is the world's most complete and best-preserved T. rex.
Cullen used a diamond-tipped coring drill to cut a cylinder of bone around the size of a battery from Sue's thigh bone -- a process he described as "nerve-wracking."