Theropod guild structure and the tyrannosaurid niche assimilation hypothesis: implications for predatory dinosaur macroecology and ontogeny in later Late Cretaceous Asiamerica¹

Well-sampled dinosaur communities from the Jurassic through early Late Cretaceous show greater taxonomic diversity among larger (>50 kg) theropod taxa than of Campano-Maastrichtian, particularly to those eastern/central Asia and Laramidia. The large carnivore guilds in Asiamerican assemblages are monopolized by tyrannosaurids, with adult medium-sized (50–500 predators rare or absent. In contrast, various clades theropods found occupy these body sizes earlier faunas, including tyrannosauroids. Assemblages “missing middle-sized” not have correspondingly sparser potential prey species recorded same faunas. niches Laramidia may been assimilated juvenile subadults tyrannosaurid species, functionally distinct their ecomorphologies. It is speculated that if tyrannosaurids previously occupied mid-sized predators, we would expect evolution transitions morphology possibly delay achievement somatic maturity this taxon.