Comparative anatomy studies of the skull of archosaurs provide insights on the mechanisms of evolution for the morphologically and functionally diverse species of crocodiles and birds. One of the key attributes of skull evolution is the anatomical changes associated with the physical arrangement of cranial bones. Here, we compare the changes in anatomical organization and modularity of the skull of extinct and extant archosaurs using an Anatomical Network Analysis approach. We show that the number of bones, their topological arrangement, and modular organization can discriminate birds from non-avian dinosaurs, and crurotarsans. We could also discriminate extant taxa from extinct species when adult birds were included. By comparing within the same framework, juveniles and adults for crown birds and alligator (Alligator mississippiensis), we find that adult and juvenile alligator skulls are topologically similar, whereas juvenile bird skulls have a morphological complexity and anisomerism more similar to those of non-avian dinosaurs and crurotarsans than of their own adult forms. Clade-specific ontogenetic differences in skull organization, such as extensive postnatal fusion of cranial bones in crown birds, can explain this pattern. The fact that juvenile and adult skulls in birds do share a similar anatomical integration suggests the presence of a specific constraint to their ontogenetic growth.

祖龙头骨的比较解剖学研究为形态和功能多样的鳄鱼和鸟类的进化机制提供了见解。头骨进化的关键属性之一是与颅骨物理排列相关的解剖学变化。在这里，我们使用解剖网络分析方法比较了已灭绝和现存古龙头骨的解剖组织和模块化的变化。我们证明，骨骼的数量、它们的拓扑排列和模块化组织可以区分鸟类与非鸟类恐龙和十字跗龙。当包括成年鸟类时，我们还可以区分现存的类群和灭绝的物种。通过在同一框架内对冠鸟和短吻鳄( Alligator mississippiensis )的幼年和成年进行比较，我们发现成年和幼年短吻鳄的头骨在拓扑结构上相似，而幼鸟的头骨具有与非鸟类更相似的形态复杂性和异构性。恐龙和十字跗龙比它们自己的成年形态要大。颅骨组织中进化枝特异性的个体发育差异，例如冠鸟出生后颅骨的广泛融合，可以解释这种模式。事实上，鸟类的幼年和成年头骨确实具有相似的解剖学整合，这表明它们的个体发育存在特定的限制。