A stage of embryogenesis in vertebrate embryos, that follows the initial stages of mesoderm differentiation and organogenesis, and which is characterized by the development of pharangeal pouches. It is during this stage of embryogenesis that all vertebrate embryos display striking similarity. The sides of the embryo head become sculptured into between six and nine columns of tissue (pharangeal arches) separated by deep slits (pharangeal grooves). In nonamniotes these structures give rise to gill slits, whilst in most tetrapods these regions give rise to the tympanic membrane, glands associated with the lymphatic system such as the thymus gland, parathyroid gland, carotid bodies, and tonsils. See also blastula; gastrula.
Subjects: Zoology and Animal Sciences.