Comparative embryological study of pectoral girdle and thorax in amniotes

甲鱼胚胎甲壳脊背、腹侧真皮分别由背侧和外侧皮神经支配，表明甲鱼胚胎背侧真皮与外侧板源性真皮之间的边界对应于甲壳脊腹侧缘，神经支配模式与细胞谱系之间的制约较小。鸡、小鼠和甲鱼的肩胛骨突起有吻突和尾突。尾突在这些动物身上形成了肩胛骨的刀片。鸡和小鼠的肩峰突起于鸡和小鼠的顶端突起，甲鱼的冠腹突起产生于甲鱼的肩峰突起，提示甲鱼胸带突起与肩峰突起同源。这一结果得到了转录因子的表达模式、与神经和肌肉原基的三维拓扑关系以及最近发现的最古老的海龟的形态的支持。小鼠肩胛骨原基在肩峰背部有额外的突起，冈上窝由其发育而来，表明该窝是羊膜中的一种新结构。

Dorsal and ventral dermis of carapacial ridge (CR) of turtle embryo were innervated by dorsal and lateral cutaneous nerve respectively, showing that there is less strict constraint between innervation pattern and cell lineage, because boundary between somite derived dermis and lateral plate derived dermis corresponds to ventral edge of the CR. In chicken, mouse and turtle, scapula anlage had rostral and caudal processes. The caudal process made a scapula blade in these animals. The rostral process gave rise to acrominal process in chick and mouse and rostro-ventral process in turtle, suggesting that the process of turtle pectoral girdle is homologous to the acromion. This result was supported by expression pattern of transcriptional factor, three dimensional topological relationships with nerve and muscle anlage and morphology of the recently discovered oldest turtle. The scapula anlage of mouse had extra process in rostro-dorsal part from which supraspinous fossa developed, showing that the fossa is novel structure among amniotes.