Modern reptiles, which are coldblooded, have three-chambered hearts, with two aortas and only one ventricle; crocodiles have two ventricles but they are incompletely separated. Thus, oxygenated blood from the lungs and deoxygenated blood from the rest of the body become mixed in these reptilian hearts, reducing the overall oxygen content of blood returned to the body and limiting the metabolic rates and activity of these animals.
''A single systemic aorta communicating with the left ventricle greatly reduces the risk of shunting and can be considered a means of more efficiently supporting prolonged periods of high activity,'' the discovery team said in its report.