T. rex Growth Extended to 40 Years via PeerJ Histology of 17 Specimens

The team prepared thin-section slices from long bones and applied polarized light microscopy plus statistical stitching of partial growth records across individuals. This composite curve replaced earlier single-specimen extrapolations that had capped adult size at 25 years. Growth remained steady rather than accelerating, implying sustained resource allocation into skeletal tissue well into the fourth decade.

Prolonged ontogeny expands the number of size-based ecological roles available within one species, reducing direct competition between cohorts and potentially stabilizing tyrannosaur dominance before the end-Cretaceous extinction. The same dataset flags several specimens previously assigned to T. rex as statistical outliers whose trajectories align more closely with contemporaneous sister taxa.

Future sampling must target femora from individuals exceeding 30 years at death; without these anchor points the upper tail of the growth curve remains sensitive to model assumptions. Larger histological datasets from other large theropods would test whether extended maturation is a tyrannosaurid clade trait or an autapomorphy of T. rex.