The vertebrate jaw is one of the essential developmental features associated with the crest cells’ changes. The history of jaws’ evolution in vertebrates can be traced to early fish species known as placoderms. Placoderms dominated the oceans, lakes, and rivers and lived for 80 million years before their extinction. However, the placoderms’ jaw bears no resemblance to today’s vertebrates, indicating that the jaw evolved into today’s vertebrate jaw. Scientific research holds that the jaw was formed from the mandibular arch, the rostralmost pharyngeal arch element. The vertebrate jaw has been a subject of study for many scholars relating the developmental features to vertebrate adaptations.
The vertebrate jaw evolved from non-jawed vertebrates that possessed pharyngeal gill apparatus. The anterior gill bars in fish are believed to have evolved into the jaw. The pharyngeal arches were undifferentiated, and their transformation in different positions led to the development of the jaw. Each position-specific differentiation is attributed to Hox genes’ transcription and endothelium signaling. The pharyngeal arches’ transformation proves the theory behind jaw evolution. Different vertebrates use the jaws for different purposes depending on the transformation involved and the structures supported by the jaw.
The jaw supports teeth and other feeding structures in vertebrates. Significant morphological changes in jaw elements include the support skeleton, patterning, loss of opercula series, and symplectic. The quadrate and articular elements in fish and reptiles’ jaws transformed into the ear bones in mammals. The jaws of early vertebrates enabled them to exploit different food types. It is strong, allowing vertebrates to use it for predation and defense. The jaw bone in mammals supports teeth formation that enables them to feed on different food types.