Hollow bones led dinosaurs to grow world's longest necks

Hollow neck bones allowed dinosaurs to evolve necks longer than any other creature that has ever lived, scientists say.
Plant-eating dinosaurs called sauropods had the longest necks in the animal kingdom. The dinosaurs' necks reached up to 50 feet (15 metres) in length, six times longer than that of the current world-record holder, the giraffe, and at least five times longer than those of any other animal that has lived on land.
In the study, researchers found that the neck bones of sauropods possessed a number of traits that supported such long necks, LiveScience reported.
For instance, air often made up 60 per cent of these animals' necks, with some as light as birds' bones, making it easier to support long chains of the bones. The muscles, tendons and ligaments were also positioned around these vertebrae in a way that helped maximise leverage, making neck movements more efficient.

In addition, the dinosaurs' giant torsos and four-legged stances helped provide a stable platform for their necks. In contrast, giraffes have relatively small torsos, while ostriches have two-legged stances.
"They [sauropods] were really stupidly, absurdly oversized. In our feeble, modern world, we're used to thinking of elephants as big, but sauropods reached 10 times the size elephants do. They were the size of walking whales," said researcher Michael Taylor, a vertebrate paleontologist at the University of Bristol in England.

To find out how sauropod necks could get so long, scientists analysed other long-necked creatures and compared sauropod anatomy with that of the dinosaurs' nearest living relatives, the birds and crocodilians.

Researchers found that sauropods also had plenty of neck vertebrae, up to 19. In contrast, nearly all mammals have no more than seven, from mice to whales to giraffes, limiting how long their necks can get.
Moreover, while pterosaur Arambourgiania had a relatively giant head with long, spear-like jaws that it likely used to help capture prey, sauropods had small, light heads that were easy to support.
These dinosaurs did not chew their meals, lacking even cheeks to store food in their mouths; they merely swallowed it, letting their guts break it down.
"Sauropod heads are essentially all mouth. The jaw joint is at the very back of the skull, and they didn't have cheeks, so they came pretty close to having Pac Man-Cookie Monster flip-top heads," researcher Mathew Wedel at the Western University of Health Sciences in Pomona, California, told the website.

The findings were detailed in the journal PeerJ.