The largest predator to ever walk on Earth may have taken a surprisingly long time to reach its massive size. A new study revealed that it may have taken Tyrannosaurus rex 35 to 40 years to become fully grown.
The team of researchers behind the study, published in PeerJ, carried out an analysis of T. rex fossils to home in on the dinosaur’s growth rate. The dinosaur bones showed that T. rex didn’t reach its full size until the age of 40, maturing for an additional 15 to 20 years longer than previously estimated.
Growth spurt
Scientists examine annual growth rings on the fossilized bones of dinosaurs to determine their age at the time of death. For the recent study, the team gathered samples of thigh and shin bones from 17 Tyrannosaurus specimens, making it the largest collection of data ever assembled on the dinosaur.
Using polarized light, the researchers were able to see previously undetected growth marks on those bones. The growth rings were not accounted for in previous studies. “Examining the growth rings preserved in the fossilized bones allowed us to reconstruct the animals’ year-by-year growth histories,” Holly Woodward, a professor of anatomy at Oklahoma State University and lead author of the new study, said in a statement.
The team was able to estimate the growth trajectory of T. rex across all stages of life in a much more detailed way. “The composite growth curve provides a much more realistic view of how Tyrannosaurus grew and how much they varied in size,” Nathan Myhrvold, a mathematician and paleobiologist at Intellectual Ventures who led the statistical analysis for the study, said in a statement.
The findings suggest that T. rex took its time in reaching adulthood, continuing to grow for four decades before reaching a size of roughly 8 tons.
Late bloomer
The new growth rate estimates could have implications for how T. rex may have spent its juvenile years. “A four-decade growth phase may have allowed younger tyrannosaurs to fill a variety of ecological roles within their environments,” Jack Horner, a researcher at Chapman University and co-author of the study, said in a statement. “That could be one factor that allowed them to dominate the end of the Cretaceous Period as apex carnivores.”
Previous studies suggested that T. rex individuals lived for about 30 years. Although it’s difficult to determine the exact age at which the species died, the new study points to a lifespan of around 45 to 50 years.
The massive predator, known for its powerful build and fatal bite, continues to surprise scientists looking to explore the life of the extinct species.
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