Data from: Craniodental functional evolution in sauropodomorph dinosaurs

Sauropodomorpha included the largest known terrestrial vertebrates and was the first dinosaur clade to achieve a global distribution. This success is associated with their early adoption of herbivory, and sauropod gigantism has been hypothesized to be a specialization for bulk feeding and obligate high-fiber herbivory. Here, we apply a combination of biomechanical character analysis and comparative phylogenetic methods with the aim of quantifying the evolutionary mechanics of the sauropodomorph feeding apparatus. We test for the role of convergence to common feeding function and divergence toward functional optima across sauropodomorph evolution, quantify the rate of evolution for functional characters, and test for coincident evolutionary rate shifts in craniodental functional characters and body mass. Results identify a functional shift toward increased cranial robustness, increased bite force, and the onset of static occlusion at the base of the Sauropoda, consistent with a shift toward bulk feeding. Trends toward similarity in functional characters are observed in Diplodocoidea and Titanosauriformes. However, diplodocids and titanosaurs retain significant craniodental functional differences, and evidence for convergent adoption of a common “adaptive zone” between them is weak. Modeling of craniodental character and body-mass evolution demonstrates that these functional shifts were not correlated with evolutionary rate shifts. Instead, a significant correlation between body mass and characters related to bite force and cranial robustness suggests a correlated-progression evolutionary mode, with positive-feedback loops between body mass and dietary specializations fueling sauropod gigantism.蜥脚形亚目（Sauropodomorpha）包含了目前已知体型最大的陆生脊椎动物，同时是首个实现全球分布的恐龙演化支。这一演化成功与其早期转向植食性生活方式息息相关，学界此前已提出假说：蜥脚类巨型化是为适应大量取食与专性高纤维植食性而演化出的特化性状。本研究结合生物力学特征分析与比较系统发育方法，旨在量化蜥脚形亚目取食结构的演化力学机制。研究中我们检验了蜥脚形亚目演化历程中，取食功能趋同至通用模式与趋异至功能最适值的作用，量化了功能特征的演化速率，并探究了颅齿功能特征与体质量是否存在同步的演化速率偏移。研究结果显示，在蜥脚类（Sauropoda）的基部类群中，出现了颅部结构强壮程度提升、咬合力增强以及静态咬合出现的功能转变，这与向大量取食的食性转变相吻合。梁龙超科（Diplodocoidea）与泰坦龙形类（Titanosauriformes）均呈现出功能特征趋于同质化的演化趋势，但梁龙科（Diplodocidae）与泰坦龙类（Titanosauria）仍存在显著的颅齿功能差异，二者之间趋同演化至共同‘适应区’的证据较为薄弱。对颅齿特征与体质量演化的建模分析表明，上述功能转变并未与演化速率偏移存在相关性。与之相反，体质量与咬合力、颅部结构强壮程度相关特征之间存在显著相关性，这提示存在协同递进的演化模式——体质量与食性特化之间的正反馈循环推动了蜥脚类巨型化的演化。