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But so far it was not clear if all dinosaurs shared this growth pattern. Was a period of extreme T. rex growth the only way dinos could grow into full adults?
A study of fossilized bone samples from 11 different dinosaurs released on Tuesday found that while some transformed during a growth spurt in adolescents, others progressed slowly and steadily.
Like tree trunks, dinosaur bones have rings that show how creatures grew and aged.
“Most animals have a period each year when they stop growing, which is traditionally suggested to be a time like winter when food is scarce. It shows up in the bones like a line, like a tree ring, ”said Tom Cullen, a science affiliate of Chicago’s Field Museum and 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 growth each year. There are also clues in the structure. bone, ”he said in a press release. .
The dinosaurs’ growth patterns depended on their families, the researchers found. T. rex and its parents, the coelurosaurs, showed a period of rapid growth during adolescence and then the growth rate would have peter once they have reached adulthood.
However, according to research, more distant cousins of T. rex could reach a similar size but grow more slowly.
The team sampled the bones of a Carcharodontosaurus, a newly identified species from Argentina. He did not reach his adult size until he was 30 and 40 and lived to be 50 or more. Despite its advanced age, it had only stopped growing for two or three years before it became part of the fossil record.
For the study, Cullen also took a sample of the Field Museum’s most famous resident dinosaur, Sue the T. rex. She lived to the age of 33 and is the most complete and best-preserved T. rex in the world.
Cullen used a diamond-tipped core drill bit to cut a stack-sized cylinder of bone from Sue’s thigh bone – a process he described as “agonizing.”
He then sliced bone samples so thin that light could pass through them. This allowed her to examine the samples under a microscope and analyze the lines showing where the new bone had grown year after year. The missing part of Sue’s leg was filled with brown putty.
Mammals, including humans, tend to undergo a growth spurt when they are young and then maintain the same size once they reach maturity. In other groups of animals, this is not always the case.
“Birds have great growth spurts and reach adulthood very quickly, while reptiles like alligators and various lizards and snakes grow for a long time.
Rapidly increasing its size can be an advantage, according to the study – it makes it easier for you to hunt other animals and harder for predators to hunt you.
Conversely, a growth spurt takes a lot of energy and resources, and it’s easier to get a little bigger each year throughout your life.
“The amount of calories T. rex would have needed during his growth spurt would have been ridiculous, ”Cullen said.
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