Research in the journal Biological Reviews presents a common sense bit of truth: The larger an animal is, the more time it spends eating. Elephants, for example, spend 18 hours per day satisfying their voracious appetites.
"This led us to one of the many riddles that gigantism of dinosaurs puts before us," said the University of Bonn's Martin Sander, who worked on the new dinosaur research. "(The dinosaurs) were just so large that a day would have had to have 30 hours so that they were able to meet their energy demands."
Since dinosaurs couldn't add hours to their daily schedule, they evolved their ability to gulp down food whole. Chewing involves a more sophisticated process, since it allows food to digest faster. When you break food down into tiny bits with your teeth, the total surface area of what's swallowed increases, permitting digestive enzymes to more easily process the food.
The main problem with chewing is that it requires a lot of time and energy. The largest sauropod plant eaters also had relatively small heads at the end of long necks. A skull permitting heavy muscle and bone, suitable for chewing, would not have worked well given such a body design. The large necks allowed the dinosaur giants to grab food with ease, instead of having to heave what was often an 80-ton body over the Jurassic savanna while looking for greens. A huge sauropod could have just stood still while moving only its neck to feed.
Sander and his team discovered that a plant called horsetail was good eats for many sauropods. The scientists determined horsetails would have been extremely nutritious for dinosaurs. Few animals dine on these plants today, however. One reason is that horsetails really do a number on teeth. They contain a lot of silicate, which acts like sandpaper. But if the consumer isn't chewing- no problem. Sauropods did have teeth, which helped with other functions, such as grabbing, and even these teeth fell out and were replaced monthly, according to the scientists.