There's no getting around it: sauropods did have small brains in their small heads. And those big bodies make the brains seem even smaller. Surprisingly, though, the brains of most living reptiles are just as small when compared to their body size. And whatever their brain size, sauropods were smart enough to be the dominant plant-eaters on the planet for 140 million years.

Elephants must feed for 18 hours a day. Sauropods could be could be 10 times elephant-size, or more, so how did they find enough hours in the day to feed? The answer may surprise you. With their tiny skulls and tiny teeth, they were huge--and hugely efficient--eating machines.

A heart is an amazing organ, whether beating in a hummingbird, a human or a sauropod. The bigger the animal, the bigger and more powerful this biological pump must be. But how big can a heart get? And how does the long sauropod neck complicate the heart's job?

Most likely you won't even recognize the lungs of Mamenchisaurus as lungs, they're so different from yours. And the lungs were just one part of a complex, highly efficient breathing system like the one found in birds today. The efficiency of this system was key to the gigantic size of sauropods.

How much food did these giants need? That depends on how much energy they used. Scientists are trying to figure out if sauropods had metabolisms more like modern mammals and birds, which need a lot of energy to sustain themselves, or like snakes, lizards and turtles, which use relatively little energy.

Long necks were a key reason sauropods were able to get so big. Long necks let the animals reach foods other plant eaters couldn't, and meant the animals could stand in one place while practically inhaling food from a large swath of landscape. But as useful as they were, long necks had some big potential downsides. One of them was immense weight.