Skeletal development in salamanders is greatly influenced by their complex life history. Although the relationship between skull development and life history has been investigated in a variety of salamander species, few studies have compared skull development among lineages. Here, we describe the cranial skeletogenesis of the Japanese giant salamander, Andrias japonicus (family Cryptobranchidae), for the first time. To conduct interspecific comparisons, we also describe the cranial skeletogenesis of Hynobius nebulosus (Hynobiidae), Pleurodeles waltl (Salamandridae) and Ambystoma mexicanum (Ambystomatidae). Our comparative analyses reveal interspecific differences in cranial skeletogenesis, particularly in the timing of the onset of ossification, the direction of ossification (e.g. from anterior to posterior) and the ossification pattern of the hyobranchial skeleton. The early onset of jaw ossification, posterior extension of the maxilla and posterolateral inclination of the squamosal in An. japonicus might be adaptations that allow An. japonicus to gulp feed, primarily using the suction force generated by opening the mouth wide, while also supplementing that force by depressing the hyobranchial skeleton. Multivariate regression of skull shape on log10-transformed centroid size revealed that the unique skull shape of adult and subadult An. japonicus forms through hypermorphosis.

中文翻译：

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最大的两栖动物之一安德里亚斯日本的颅骨骨骼发育提供了洞察蝾螈喂养的个体发育适应

蝾螈的骨骼发育很大程度上受其复杂的生活史的影响。尽管已经在各种蝾螈物种中研究了头骨发育与生活史之间的关系，但很少有研究比较不同血统的头骨发育。在这里，我们首次描述了日本大蝾螈 Andrias japonicus（隐鳃科）的颅骨形成。为了进行种间比较，我们还描述了 Hynobius nebulosus (Hynobiidae)、Pleurodeles waltl (Salamandridae) 和 Ambystoma mexicanum (Ambystomatidae) 的颅骨骨骼形成。我们的比较分析揭示了颅骨骨骼形成的种间差异，特别是在骨化开始的时间，骨化的方向（例如 从前到后）和肱骨的骨化模式。An中颌骨骨化的早期发作，上颌骨的后伸和鳞状骨的后外侧倾斜。japonicus 可能是允许 An. 日本海参吸食，主要是利用张开嘴产生的吸力，同时还通过压下鳃骨来补充这种吸力。颅骨形状对 log10 变换质心大小的多元回归揭示了成人和亚成人 An 独特的头骨形状。japonicus 通过变形形成。主要利用张开嘴巴产生的吸力，同时还通过压下下颌骨来补充这种吸力。颅骨形状对 log10 变换质心大小的多元回归揭示了成人和亚成人 An 独特的头骨形状。japonicus 通过变形形成。主要利用张开嘴巴产生的吸力，同时还通过压下下颌骨来补充这种吸力。颅骨形状对 log10 变换质心大小的多元回归揭示了成人和亚成人 An 独特的头骨形状。japonicus 通过变形形成。