(A) In the mammalian embryo, NC cells delaminate form the dorsal neural tube and migrate in a stereotypical pattern. Based on their origin in the hindbrain (arrows) they populate individual pharyngeal arches (PA). The cardiac NC (red arrows) arises from a region posterior to the otic vesicle (OV) and migrates through pharyngeal arches 3, 4 and 6, along the aortic arch arteries (AA) and into the outflow tract (OFT) of the heart (red circles) to form the aorticopulmonary septum. There are no fifth pharyngeal arch arteries in amniotes. Lateral view, anterior to left, dorsal to top. (B) In chick and mouse the cardiac NC contributes to aortic arch arteries and forms the aorticopulmonary septum of the outflow tract. In Xenopus, cardiac NC cells populate the aortic sac and arch arteries, but do not colonize the outflow tract septum.