New study revises T. rex growth timeline, reached full size by 35–40 years
A study of 17 Tyrannosaurus rex fossils using polarized light reveals growth rings showing they grew slowly, not reaching a maximum size of about 8 tons until about 35–40 years old. Growth rings capture only the last 10–20 years of life, but by combining data across ages researchers reconstructed year-by-year growth, finding more variability and suggesting possible taxonomic differences such as Nanotyrannus; the findings revise the dinosaur’s growth timeline and how it occupied various ecological niches.