 It is possible to measure the minimum blood pressures of dinosaurs by estimating the vertical distance between the heart and the top of the head, because this column of blood must have a pressure at the bottom equal to the hydrostatic pressure derived from the density of blood and gravity.Added to this pressure is that required to move the blood through the circulatory system.It was pointed out in 1976 that, because of their height, many dinosaurs had minimum blood pressures within the endothermic range, and that they must have had four-chambered hearts to separate the high pressure circuit to the body from the low pressure circuit to the lungs.