Fig. 10

Cartoon depicting the results of aorto-pulmonary septation and PAA remodelling in crocodilians, birds and mammals. a In reptiles, represented here by the crocodile, the visceral (left PAA4) and systemic aorta (right PAA4) are separated by the aorto-aortic flow divider (light yellow), while the pulmonary trunk (PAA6) is separated from both aortae by the AP septum (green, *). The pulmonary flow divider (dark yellow) is not involved in aorto-pulmonary separation. b In birds, the left PAA4 disappears and the aortic flow divider merges with the AP septum. c In mammals, both PAA4 persist, but the right PAA6 disappears and the pulmonary flow divider merges with the AP septum. In birds, the aorto-pulmonary septal complex results from the merging of the neural crest-derived AP septum with the aortic flow divider and in mammals from the AP septum with the pulmonary flow divider. *AP septum, 3, 4, 6 PAAs by number; cd carotid duct, dAo dorsal Aorta, pa pulmonary artery, sa subclavian artery, vAo visceral aorta; Left left side; Right right side