Benson adds that since larger animals can lay more eggs and reproduce more quickly, there may have been a reproductive advantage to being big.
Brian McNab, a professor of zoology at the University of Florida, has also studied dinosaur growth trends. He thinks the biggest dinos ate often and moved little.
"The large herbivorous dinosaurs undoubtedly spent much of their day feeding," McNab told Discovery News. "One should notice that the heads of dinosaurs related to the size of the bodies were very small, which means that the dinosaurs spent little time chewing the food, so most processing occurred in the gut, therefore the process of eating was probably inexpensive."
"This is very different from the behavior of most herbivorous mammals, which have large heads that house many teeth and spend much time chewing," McNab explained.
Benson thinks it's unlikely that any land animals today, including humans, could ever evolve to become as large as the biggest dinosaurs were.
"Mammals, including humans, are warm-blooded and generate a lot of heat internally," he explained. "This becomes a problem at large body sizes as there is a danger of overheating. It's possible that many extinct archosaurs, including dinosaurs, were intermediate between cold-blooded and warm-blooded physiologies."