http://en.wikipedia.org/wiki/Pharyngeal_slit
In vertebrates, the pharyngeal arches are derived from all three germ layers.Neural crest cells enter these arches where they contribute to craniofacial features such as bone and cartilage.However, the existence of pharyngeal structures before neural crest cells evolved is indicated by the existence of neural crest-independent mechanisms of pharyngeal arch development.
In vertebrates, the pharyngeal arches are derived from all three germ layers.Neural crest cells enter these arches where they contribute to craniofacial features such as bone and cartilage.However, the existence of pharyngeal structures before neural crest cells evolved is indicated by the existence of neural crest-independent mechanisms of pharyngeal arch development.
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