by Eric Powell
Generations of dinosaur enthusiasts have been raised on images of gigantic sauropod dinosaurs gracefully elevating their snakelike necks to munch on Mesozoic treetops or rearing back to intimidate predators. But Roger Seymour, a comparative physiologist at the University of Adelaide in South Australia, says that these majestic behemoths probably never held their heads up high for a pressing reason: heart problems.
Seymour, an expert in the evolution of vertebrate cardiovascular systems, studied Barosaurus, a relative of Apatosaurus (formerly known as Brontosaurus) to infer how its circulatory system worked. The animal would have needed mind-bogglingly high blood pressure— about seven times as high as in humans— to send fluids to a head raised up all the way. According to Seymour's calculations, such an elevated blood pressure would have required an improbably large heart. The left ventricle alone would have weighed two tons— about 5 percent of the creature's ...
