Crocodylomorpha, which includes living crocodylians and their extinct relatives, has a rich fossil record, extending back for more than 200 million years. Unlike modern semi-aquatic crocodylians, extinct crocodylomorphs exhibited more varied lifestyles, ranging from marine to fully terrestrial forms. This ecological diversity was mirrored by a remarkable morphological disparity, particularly in terms of cranial morphology, which seems to be closely associated with ecological roles in the group. Here, I use geometric morphometrics to comprehensively investigate cranial shape variation and disparity in Crocodylomorpha. I quantitatively assess the relationship between cranial shape and ecology (i.e. terrestrial, aquatic, and semi-aquatic lifestyles), as well as possible allometric shape changes. I also characterise patterns of cranial shape evolution and identify regime shifts. I found a strong link between shape and size, and a significant influence of ecology on the observed shape variation. Terrestrial taxa, particularly notosuchians, have significantly higher disparity, and shifts to more longirostrine regimes are associated with large-bodied aquatic or semi-aquatic species. This demonstrates an intricate relationship between cranial shape, body size and lifestyle in crocodylomorph evolutionary history. Additionally, disparity-through-time analyses were highly sensitive to different phylogenetic hypotheses, suggesting the description of overall patterns among distinct trees. For crocodylomorphs, most results agree in an early peak during the Early Jurassic and another in the middle of the Cretaceous, followed by nearly continuous decline until today. Since only crown-group members survived through the Cenozoic, this decrease in disparity was likely the result of habitat loss, which narrowed down the range of crocodylomorph lifestyles.

中文翻译：

---

鳄形颅骨形态演变及其与体型和生态的关系

包括活鳄鱼和已灭绝的亲属在内的鳄形目拥有丰富的化石记录，可追溯到2亿多年。与现代的半水生鳄类不同，绝种的鳄形生物表现出更多的生活方式，从海洋到陆生的形式。这种生态多样性反映了显着的形态差异，特别是在颅的形态方面，这似乎与该群体中的生态作用密切相关。在这里，我使用几何形态计量学全面研究了鳄形的颅骨形状变化和差异。我定量评估了颅骨形状与生态学（即陆生，水生和半水生生活方式）之间的关系，以及可能的异形体变化。我还描述了颅骨形状演变的模式并确定了政权转移。我发现形状和大小之间有很强的联系，并且生态学对观察到的形状变化有重大影响。陆地生物分类，特别是nososuchian，具有更大的差异，并且向更大的水松或半水生物种转移到更长的长曲链素状态。这表明鳄形进化史中颅骨形状，体型和生活方式之间存在复杂的关系。此外，时差分析对不同的系统发育假设高度敏感，这表明对不同树木之间总体模式的描述。对于鳄形类动物，大多数结果都在侏罗纪早期和白垩纪中期达到了一个峰值。随后直到今天几乎持续下降。由于只有冠群成员通过新生代得以幸存，因此这种差异的减少很可能是栖息地丧失的结果，这缩小了鳄形生活的范围。