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.
It is created as the second pharyngeal arch (hyoid arch) grows more rapidly than the other pharyngeal arches, causing them to be enveloped. The first pharyngeal arch (mandibular arch) also develops slightly faster.