The independent evolution of gigantism among dinosaurs has been a topic of longstanding interest, but it remains unclear if gigantic theropods, the largest bipeds in the fossil record, all achieved massive sizes in the same manner, or through different strategies. We perform multi-element histological analyses on a phylogenetically broad dataset sampled from eight theropod families, with a focus on gigantic tyrannosaurids and carcharodontosaurids, to reconstruct the growth strategies of these lineages and test if particular bones consistently preserve the most complete growth record. We find that in skeletally-mature gigantic theropods, weightbearing bones consistently preserve extensive growth records, whereas non-weightbearing bones are remodelled and less useful for growth reconstruction, contrary to the pattern observed in smaller theropods and some other dinosaur clades. We find a heterochronic pattern of growth fitting an acceleration model in tyrannosaurids, with allosauroid carcharodontosaurids better fitting a model of hypermorphosis. These divergent growth patterns appear phylogenetically constrained, representing extreme versions of the growth patterns present in smaller coelurosaurs and allosauroids, respectively. This provides the first evidence of a lack of strong mechanistic or physiological constraints on size evolution in the largest bipeds in the fossil record, and evidence of one of the longest-living individual dinosaurs ever documented.

Data consist of images of fossil bone thin-sections. They were collected using standard paleohistology methods. See Cullen et al 2020 and references therein for detailed methodology

Data include high-resolution thin-section images used in analyses in Cullen et al 2020 (Histological dataset for: osteohistological analyses reveal diverse strategies of theropod dinosaur body-size macroevolution). Please see publication for further details of specimens.