Giant Dinosaurs Stuck Their Necks Out, Not Up?

Long-necked dinosaurs didn't graze treetops, according to new research that suggests the prehistoric animals were better off holding their necks horizontal, not upright.

Lifting long necks at steep angles would have put intense pressure on sauropod hearts, requiring dramatic expenditures of energy to keep blood pumping to the brain, a new study of dinosaur circulation says.

Sauropods were giant, long-necked, long-tailed, four-legged plant-eaters that lived about 200 to 66 million years ago (prehistoric time line).

Since long-necked modern animals, such as giraffes, tend to browse on leaves in tall trees, paleontologists have assumed that sauropods—whose necks could be as long as 30 feet [9 meters]—must have done the same.

But Roger Seymour, of the University of Adelaide in Australia, found that sauropods would have spent as much as 75 percent of their bodies' energy to keep their heads held high.

Most mammals use about 10 percent of their energy to circulate blood through their bodies. Giraffes use about 18 percent of their energy to keep blood moving through their long, upright necks.

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