Multiple pathways to herbivory underpinned deep divergences in ornithischian evolution

Area of Science:

• Paleontology
• Evolutionary Biology
• Biomechanics

Background:

• The predictability of evolution is a central question, with adaptation and constraints potentially guiding evolutionary trajectories.
• Fossil data is crucial for understanding past evolution, but biomechanical performance data for extinct species is scarce.
• Ornithischian dinosaurs, with multiple independent origins of herbivory, offer a unique model for studying evolutionary responses to similar ecological pressures.

Purpose of the Study:

• To investigate the morphofunctional pathways to herbivory in early-diverging ornithischian dinosaurs.
• To compare biomechanical performance and adaptations of the feeding apparatus across different ornithischian clades that evolved herbivory independently.

Main Methods:

• Finite-element analysis was performed on the skulls of five early-diverging ornithischian taxa.
• The study reconstructed patterns and magnitudes of functionally induced stress during feeding.

Main Results:

• Limited functional convergence was observed among the studied ornithischian clades.
• Each clade achieved comparable feeding performance through distinct adaptations: thyreophorans increased size, heterodontosaurids enlarged jaw muscles, ornithopods enhanced jaw system efficiency, and ceratopsians combined these strategies.
• These varied solutions highlight diverse evolutionary pathways to herbivory within Ornithischia.

Conclusions:

• The evolution of herbivory in ornithischian dinosaurs was not a predictable, convergent process.
• Distinct morphofunctional adaptations allowed different clades to overcome similar ecological challenges, demonstrating evolutionary flexibility.
• Phenotypic evolution arises from a complex interplay of adaptation, innovation, contingency, and constraints, underscoring the unpredictable nature of macroevolutionary outcomes.