Data from: Morphological and biomechanical disparity of crocodile-line archosaurs following the end-Triassic extinction

Mesozoic crurotarsans exhibited diverse morphologies and feeding modes, representing considerable ecological diversity, yet macroevolutionary patterns remain unexplored. Here we employ a unique combination of morphological and biomechanical disparity metrics to quantify the ecological diversity and trophic radiations of Mesozoic crurotarsans, using the mandible as a morpho-functional proxy. We recover three major trends. First, the diverse assemblage of Late Triassic crurotarsans was morphologically and biomechanically disparate, implying high levels of ecological variation; but, following the end-Triassic extinction, disparity declined. Second, the Jurassic radiation of marine thalattosuchians resulted in very low morphological disparity but moderate variation in jaw biomechanics, highlighting a hydrodynamic constraint on mandibular form. Third, during the Cretaceous terrestrial radiations of neosuchians and notosuchians, mandibular morphological variation increased considerably. By the Late Cretaceous, crocodylomorphs evolved a range of morphologies equaling Late Triassic crurotarsans. In contrast, biomechanical disparity in the Cretaceous did not increase, essentially decoupling from morphology. This enigmatic result could be attributed to biomechanical evolution in other anatomical regions (e.g. cranium, dentition or postcranium), possibly releasing the mandible from selective pressures. Overall, our analyses reveal a complex relationship between morphological and biomechanical disparity in Mesozoic crurotarsans that culminated in specialized feeding ecologies and associated lifestyles.

中生代嵌跗类鳄形（Crurotarsi）展现出多样的形态构型与取食模式，体现出可观的生态多样性，但其大演化格局迄今尚未被探明。本研究结合独特的形态学与生物力学差异度（disparity）指标，以下颌作为形态功能替代指标，量化了中生代嵌跗类鳄形的生态多样性与营养辐射演化过程。我们得到三大主要趋势。其一，三叠纪晚期的嵌跗类鳄形类群在形态学与生物力学层面均呈现出较高的差异度，暗示其生态变异程度较高；但在三叠纪末灭绝事件发生后，差异度出现了下降。其二，侏罗纪海洋海鳄亚目（Thalattosuchia）的辐射演化虽带来了极低的形态差异度，但其下颌生物力学特征却存在中等程度的变异，这凸显出下颌形态受到流体力学约束。其三，在白垩纪陆生真鳄类（Neosuchia）与诺托鳄类（Notosuchia）的辐射演化过程中，下颌的形态变异程度显著提升。至白垩纪晚期，鳄形类演化出的形态范围可与三叠纪晚期的嵌跗类鳄形相媲美。与之形成鲜明对比的是，白垩纪的生物力学差异度并未出现提升，本质上与形态演化脱钩。这一令人费解的结果或许可归因于其他解剖区域（如颅骨、齿列或躯干骨骼）的生物力学演化，这可能使下颌摆脱了选择压力。总体而言，本研究的分析结果揭示了中生代嵌跗类鳄形在形态学与生物力学差异度之间存在复杂的关联，这种关联最终催生了特化的取食生态与相应的生活方式。