Reif W E
J Morphol. 1980 Dec;166(3):275-88. doi: 10.1002/jmor.1051660303.
Serial sections ranging from very young embryos to hatched juveniles and whole embryos of Scyliorhinus show that dentition and dermal skeleton belong to two independent secondary developmental fields that differ both developmentally and structurally. The development of the dentition starts very early, with a thickening of the ectoderm in the region of the mouth (stage 04), the invagination of the dental lamina (stage 18), and the formation of the germs of the first generation (stage 20). Tooth replacement movements start only near the end of embryogenesis (stage 35). Scale germs, on the other hand, first begin to form at stage 24. Scales erupt shortly before the animal hatches (stage 43). Only one scale generation is formed during embryogenesis. The forces which erupt the scales may come from fluid pressures in vacuoles of the fibrous layer of the dermis. Those which erupt the teeth probably also result from similar fluid pressures. The crown and upper part of the base of scales and teeth are formed by cells of the inner dental epithelium which are differentiated from the ectoderm. They are also formed by odontoblasts which are derived from the vascular layer of the dermis. However, the basal plates of scales and teeth containing the anchoring fibers are formed by osteoblasts, which are derived from the fibrous layer of the dermis.
对斑鳐从非常幼小的胚胎到孵化出的幼体以及整个胚胎进行的连续切片显示，牙齿和真皮骨骼属于两个独立的次生发育领域，在发育和结构上均有所不同。牙齿的发育开始得非常早，在口部区域外胚层增厚（第04阶段），牙板内陷（第18阶段），以及第一代牙胚形成（第20阶段）。牙齿替换运动仅在胚胎发育接近尾声时（第35阶段）开始。另一方面，鳞片芽在第24阶段开始首次形成。鳞片在动物孵化前不久（第43阶段）长出。胚胎发育期间仅形成一代鳞片。使鳞片长出的力量可能来自真皮纤维层液泡中的流体压力。使牙齿长出的力量可能也源于类似的流体压力。鳞片和牙齿的冠部以及基部上部由从外胚层分化而来的内牙上皮细胞形成。它们也由源自真皮血管层的成牙本质细胞形成。然而，包含锚定纤维的鳞片和牙齿的基板由成骨细胞形成，而成骨细胞源自真皮的纤维层。
