It is formed as the second pharyngeal arch (hyoid arch) grows faster than the other pharyngeal arches, so they become covered. The first pharyngeal arch (mandibular arch) also grows slightly faster.
The structure develops in a manner that the second pharyngeal arch (hyoid arch), which grows at a greater pace than the other arches, becomes encased. Meanwhile, the first pharyngeal arch (mandibular arch) experiences slightly accelerated growth.