The Foramen of Panizza is a hole with a valve that connects the left and right aorta in the crocodilian heart. Crocodilians have a completely separated ventricle with deoxygenated blood from the body, or systemic circulation in the right ventricle and oxygenated blood from the lungs, or pulmonary circulation in the left ventricle, as in birds and mammals. Crocodilians have both a left and pulmonary aorta leaving the right ventricle. Blood can flow from the right ventricle back to systemic circulation through the left aortic arch. The Foramen of Panizza connects the left and right aorta, and oxygenated blood can flow into the left aorta or deoxygenated blood can flow into the right aorta through the foramen.