In museums all over the world, skeletons of sauropod dinosaurs are reconstructed with their heads held high. It seems like the most natural position for these animals, but a short letter recently published in Science has questioned whether it is correct. According to biologist Roger Seymour, sauropods more likely kept their heads low to the ground, swinging them from side to side to vacuum up plant food.
The problem with sauropod posture is that their necks are ludicrously long. It would take a huge amount of blood pressure, generated by a massive heart, to keep blood pumping to the brain. This would be made all the more difficult if the animals held their heads high in the air, as the blood flow would have to work against gravity. For this reason Seymour favors the idea that sauropods kept their heads down and mostly moved them horizontally.
In a reply, paleontologists P. Martin Sander, Andreas Christian and Carole Gee agree that sauropods may have preferentially kept their heads at a relatively low level, but it was still possible that sauropods raised their heads high. That sauropods could do so is known from skeletal evidence, and it is possible that sauropods had physiological mechanisms to solve this problem that are not seen in living animals. It would take a lot of energy for a sauropod to raise its neck up high, but if the food it was reaching was high quality, or provided a large nutritional benefit, the reward might be worth the stress. The ability of sauropods to reach up high may have even benefited them during harsh conditions, when they could physically reach a wider array of resources than other dinosaurs.
Unfortunately, much of how sauropods used their necks, particularly in feeding, remains contentious. So much of the debate rests upon sauropod physiology that without a living animal to study the arguments will continue. That is what makes for compelling science, though, and who knows what new discoveries might shed light on this old problem.