Disparate feeding mechanics between two hadrosaurid dinosaurs support the potential for resource partitioning

The Dinosaur Park Formation (DPF) of western Canada is well known for its diverse fossil assemblage, preserving over a dozen species of large-bodied herbivorous dinosaurs. The high density of large herbivores has raised questions of how these animals were able to coexist and limit competition, leading to several studies investigating the potential for resource partitioning. In the DPF, hadrosaurids are of particular ecological significance because of their abundance, diversity, and complex feeding system. Here, we used 3D muscle reconstructions and finite element analysis to evaluate the mechanical performance of the cranium and lower jaws of the lambeosaurine Corythosaurus casuarius and the contemporaneous hadrosaurine Gryposaurus notabilis to test for the potential of resource partitioning. We found G. notabilis had larger adductor muscles than similarly sized C. casuarius, but the latter had greater mechanical efficiency, resulting in similar bite forces for similarly sized animals. The cranium of C. casuarius is more resistant to bending than G. notabilis, and exhibits a derived stress distribution likely associated with the supracranial crest. Resource partitioning between these taxa would have been primarily size-mediated, where larger G. notabilis would have been able to processes tougher plant material than smaller C. casuarius at equivalent ontogenetic stages.

加拿大西部的恐龙公园组（Dinosaur Park Formation，DPF）以其多样的化石组合闻名，保存了十余种大型植食性恐龙物种。大型植食动物的高密度分布引发了学界对这些物种如何共存并缓解种间竞争的探讨，由此催生了多项围绕资源分隔潜力展开的研究。在DPF中，鸭嘴龙科（hadrosaurids）凭借其丰度、多样性与复杂的取食系统，具备特殊的生态重要性。本研究采用三维肌肉重建与有限元分析技术，对赖氏龙亚科（lambeosaurine）冠龙（Corythosaurus casuarius）以及同时代鸭嘴龙亚科（hadrosaurine）格里芬龙（Gryposaurus notabilis）的颅骨与下颌的力学性能进行评估，以检验二者间存在资源分隔的可能性。研究结果显示，体型相近的格里芬龙拥有比冠龙更大的颌收肌群（adductor muscles），但冠龙的机械效率更高，因此体型相近的个体具备相近的咬合力。冠龙的颅骨相较于格里芬龙更耐弯曲，且呈现出与颅顶脊（supracranial crest）相关的衍生应力分布模式。这两类恐龙之间的资源分隔主要由体型介导：在相同个体发育阶段，体型更大的格里芬龙能够处理比体型更小的冠龙更为坚韧的植物性食物。