T. rex grew to adulthood over four decades, new study finds
A large study of 17 tyrannosaur fossils using expanded histology and advanced statistics finds Tyrannosaurus rex reached its adult mass of about eight tons after roughly 40 years, slower and more variable than previously thought. The work uncovers previously overlooked growth rings, suggests a longer subadult phase, and raises questions about whether some specimens (including Jane and Petey) belong to a separate Nanotyrannus-like species, reshaping debates about tyrannosaur growth and diversity.