T rex took about 40 years to reach its full size, study finds

A new study of 17 tyrannosaur specimens used imaging and an algorithm to count hidden growth rings and found Tyrannosaurus rex reached full size over roughly 40 years, extending previous estimates of about 25 years.

Tyrannosaurus rex appears to have grown more slowly and over a longer period than earlier studies indicated. Researchers analysed bone slices from 17 tyrannosaur specimens, ranging from early juveniles to large adults. They used a special light technique and an algorithm to reveal and count previously hidden growth rings. The study reports that T rex reached full size of around eight tonnes after about 40 years. Key findings: - The team assembled the largest data set yet for Tyrannosaurus, with 17 specimens covering multiple life stages. - Imaging under special lighting plus an objective algorithm revealed additional annual growth rings in fossil leg bones. - A composite growth curve built from multiple individuals indicates a growth period of about 40 years, roughly 15 years longer than some earlier estimates near 25 years. - The results imply a prolonged subadult phase, which could have allowed younger tyrannosaurs to occupy varied ecological roles. - The authors note that some specimens long assigned to T rex might belong to other tyrannosaur species, a topic that remains debated. Summary: The study revises the growth timeline for Tyrannosaurus rex toward a more gradual, four-decade trajectory and raises questions about species assignments among known specimens. The authors argue that common methods for dinosaur bone growth studies may need revision and present an algorithmic approach as an alternative. Undetermined at this time.