Laboratory for Evolutionary Morphology, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Hyogo, Japan; Evolutionary Morphology Laboratory, RIKEN Cluster for Pioneering Research (CPR), Kobe, Hyogo, Japan.
Curr Top Dev Biol. 2021;141:207-239. doi: 10.1016/bs.ctdb.2020.11.011. Epub 2020 Dec 13.
Modern vertebrates consist of two sister groups: cyclostomes and gnathostomes. Cyclostomes are a monophyletic jawless group that can be further divided into hagfishes and lampreys, which show conspicuously different developmental and morphological patterns. However, during early pharyngula development, there appears to be a stage when the embryos of hagfishes and lampreys resemble each other by showing an "ancestral" craniofacial pattern; this pattern enables morphological comparison of hagfish and lamprey craniofacial development at late stages. This cyclostome developmental pattern, or more accurately, this developmental pattern of the jawless grade of vertebrates in early pharyngula was very likely shared by the gnathostome stem before the division of the nasohypophyseal placode led to the jaw and paired nostrils. The craniofacial pattern of the modern jawed vertebrates seems to have begun in fossil ostracoderms (including galeaspids), and was completed by the early placoderm lineages. The transition from jawless to jawed vertebrates was thus driven by heterotopy of development, mainly caused by separation and shift of ectodermal placodes and resultant ectomesenchymal distribution, and shifts of the epithelial-mesenchymal interactions that underlie craniofacial differentiation. Thus, the evolution of the jaw was not a simple modification of the mandibular arch, but a heterotopic shift of the developmental interactions involving not only the mandibular arch, but also the premandibular region rostral to the mandibular arch.
圆口类和有颌类。圆口类是一个单系的无颌类群，可进一步分为七鳃鳗和盲鳗，它们表现出明显不同的发育和形态模式。然而，在早期咽胚发育过程中，似乎有一个阶段，七鳃鳗和盲鳗的胚胎通过表现出一种“祖先”的颅面模式而彼此相似；这种模式使得可以对七鳃鳗和盲鳗颅面发育的晚期阶段进行形态比较。这种圆口类发育模式，或者更准确地说，这种无颌类脊椎动物早期咽胚的发育模式，很可能在鼻垂体嵴板分裂导致颌和成对鼻孔之前，就已经被有颌类脊椎动物的祖先进化所共享。现代有颌脊椎动物的颅面模式似乎始于化石盔甲鱼（包括盔甲鱼），并在早期盾皮鱼类谱系中完成。从无颌到有颌脊椎动物的过渡是由发育的异位驱动的，主要是由于外胚层嵴板的分离和移位以及由此产生的外胚间充质分布的变化，以及为颅面分化提供基础的上皮-间充质相互作用的变化。因此，颌的进化不是下颌弓的简单修饰，而是涉及下颌弓以及下颌弓前方的前下颌区的发育相互作用的异位转移。
