In principle one would expect dinosaurs to have had two-part circulations driven by four-chambered hearts, since many would have needed high blood pressure to deliver blood to their heads, which were high off the ground, but vertebrate lungs can only tolerate fairly low blood pressure.
U principu se moglo očekivati da su dinosauri imali dvodijelnu cirkulaciju kojom je upravljalo četverodijelno srce, budući da bi mnogi trebali visok krvni pritisak kako bi krv došla do njihovih glava, koje su bile visoko iznad tla, ali pluća kralježnjaka mogu tolerirati samo vrlo nizak krvni pritisak.