The evolution of the jaw represents a key innovation in driving the diversification of vertebrate body plans and behavior. The pharyngeal apparatus originated as gill bars separated by slits in chordate ancestors to vertebrates. Later, with the acquisition of neural crest, pharyngeal arches gave rise to branchial basket cartilages in jawless vertebrates (agnathans), and later bone and cartilage of the jaw, jaw support, and gills of jawed vertebrates (gnathostomes). Major events in the evolution of jaw structure from agnathans to gnathostomes include axial regionalization of pharyngeal elements and formation of a jaw joint. Hox genes specify the anterior–posterior identity of arches, and edn1, dlx, hand2, Jag1b‐Notch2 signaling, and Nr2f factors specify dorsal–ventral identity. The formation of a jaw joint, an important step in the transition from an un‐jointed pharynx in agnathans to a hinged jaw in gnathostomes involves interaction between nkx3.2, hand2, and barx1 factors. Major events in jaw patterning between fishes and reptiles include changes to elements of the second pharyngeal arch, including a loss of opercular and branchiostegal ray bones and transformation of the hyomandibula into the stapes. Further changes occurred between reptiles and mammals, including the transformation of the articular and quadrate elements of the jaw joint into the malleus and incus of the middle ear. Fossils of transitional jaw phenotypes can be analyzed from a developmental perspective, and there exists potential to use genetic manipulation techniques in extant taxa to test hypotheses about the evolution of jaw patterning in ancient vertebrates.

中文翻译：

---

鱼颚骨的演变和发展。

颌骨的进化代表了推动脊椎动物身体计划和行为多样化的一项关键创新。咽部器官起源于g条，在g裂祖先的缝隙中被分隔开来。后来，随着神经c的获得，咽弓在无颌脊椎动物中（agnathans）引起了branch状软骨，随后在颌骨的骨骼和软骨，颌骨支持物和颌骨脊椎动物的腮中产生了软骨（gnathostomes）。颌骨结构从棘突到棘突的演变过程中的主要事件包括咽部元件的轴向区域化和颌关节的形成。Hox基因指定了足弓的前后身份，以及edn1，dlx，hand2，Jag1b-Notch2信号和Nr2f因子指定背腹身份。颌关节的形成，这是从agnathans中未连接的咽部过渡到gnastostomes中的铰接式下颌的重要步骤，涉及nkx3.2，hand2和barx1之间的相互作用。因素。鱼类和爬行动物之间的下颌形态重大事件包括第二咽弓弓的元素变化，包括舌骨和branch骨骨的射线骨丢失以及hy胫骨变成sta骨。爬行动物和哺乳动物之间发生了进一步的变化，包括下颌关节的关节和四边形元素转换为中耳的锤骨和砧骨。过渡颌表型的化石可以从发展的角度进行分析，并且有可能在现存的生物分类中使用遗传操纵技术来检验关于古代脊椎动物颌模式演变的假说。