Science. 1983 Apr 15;220(4594):268-73. doi: 10.1126/science.220.4594.268.
Most of the morphological and functional differences between vertebrates and other chordates occur in the head and are derived embryologically from muscularized hypomere, neural crest, and epidermal (neurogenic) placodes. In the head, the neural crest functions as mesoderm and forms connective, skeletal, and muscular tissue. Both the neural crest and the epidermal placodes form special sense organs and other neural structures. These structures may be homologous to portions of the epidermal nerve plexus of protochordates. The transition to vertebrates apparently was associated with a shift from a passive to an active mode of predation, so that many of the features occurring only in vertebrates became concentrated in the head.
脊椎动物和其他脊索动物之间的大多数形态和功能差异都发生在头部，并且在胚胎发生上源自肌肉化的基板、神经嵴和表皮（神经原性）基板。在头部，神经嵴充当中胚层，并形成结缔组织、骨骼和肌肉组织。神经嵴和表皮基板都形成特殊的感觉器官和其他神经结构。这些结构可能与原索动物表皮神经丛的部分同源。向脊椎动物的转变显然与从被动捕食向主动捕食的模式转变有关，因此，许多仅在脊椎动物中出现的特征集中在头部。
