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| Life reconstruction of the Late Cretaceous Iren Dabasu Formation fauna, Inner Mongolia, showing theropod dinosaurs of various diets. Such dietary niche partitioning could have contributed to the diversification of theropod dinosaurs, which eventually led to the evolution of modern birds. Depicted species: Gigantoraptor, Neimongosaurus and Velociraptor. in Ma, Pittman, Butler & Lautenschlager, 2021. |
Highlights:
• A general trend of jaw strengthening is observed along all theropod lineages
• Carnivores and herbivores achieved this via different morphofunctional modifications
• Same jaw strengthening trend is also detected in tyrannosaurids ontogenetically
• This common trend is linked to functional peramorphosis of bone functional adaptation
Summary
Theropod dinosaurs underwent some of the most remarkable dietary changes in vertebrate evolutionary history, shifting from ancestral carnivory to hypercarnivory and omnivory/herbivory, with some taxa eventually reverting to carnivory. The mandible is an important tool for food acquisition in vertebrates and reflects adaptations to feeding modes and diets. The morphofunctional modifications accompanying the dietary changes in theropod dinosaurs are not well understood because most of the previous studies focused solely on the cranium and/or were phylogenetically limited in scope, while studies that include multiple clades are usually based on linear measurements and/or discrete osteological characters. Given the potential relationship between macroevolutionary change and ontogenetic pattern,23 we explore whether functional morphological patterns observed in theropod mandibular evolution show similarities to the ontogenetic trajectory. Here, we use finite element analysis to study the mandibles of non-avialan coelurosaurian theropods and demonstrate how feeding mechanics vary between dietary groups and major clades. We reveal an overall reduction in feeding-induced stresses along all theropod lineages through time. This is facilitated by a post-dentary expansion and the development of a downturned dentary in herbivores and an upturned dentary in carnivores likely via the “curved bone effect.” We also observed the same reduction in feeding-induced stress in an ontogenetic series of jaws of the tyrannosaurids Tarbosaurus and Tyrannosaurus, which is best attributed to bone functional adaptation. This suggests that this common tendency for structural strengthening of the theropod mandible through time, irrespective of diet, is linked to “functional peramorphosis” of bone functional adaptations acquired during ontogeny.
Keywords: dinosaur, functional morphology, feeding mechanics, diet, skull, peramorphosis, mesozoic, vertebrate palaeontology
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| Life reconstruction of the Late Cretaceous Iren Dabasu Formation fauna, showing theropod dinosaurs of various diets. Such dietary niche partitioning could have contributed to the diversification of theropod dinosaurs, which eventually led to the evolution of modern birds. Depicted species: Gigantoraptor, Garudimimus, Neimongosaurus and Velociraptor. Artwork: Gabriel Ugueto. |
Waisum Ma, Michael Pittman, Richard J. Butler and Stephan Lautenschlager. 2021. Macroevolutionary Trends in Theropod Dinosaur Feeding Mechanics. Current Biology. In Press. DOI: 10.1016/j.cub.2021.11.060
