Sauropods were the largest creatures ever to live on land. One of the largest species found to date, Supersaurus, weighed upwards of 80,000 pounds. The suborder Sauropoda contains other heavy-weights such as Brachiosaurus, Apatosaurus, and Diplodocus. Roughly ten times the size of an elephant, sauropods more closely resembled whales in sheer size. Besides their immense weight, sauropods are also known for their elongated necks. The Supersaurus boasted a neck 50 feet long.
Not many animals have evolved long necks since the sauropods, and none have done it so well. The longest neck of any living animal today is that of the adult male giraffe, which can reach eight feet in length. A distant second, the ostrich, has up to three feet of neck. Why such few notable necks today? Living with a long neck isn’t easy.
One drawback of a lengthy throat is the difficulty it poses to breathing. For a mammal, like the giraffe, who has to draw oxygen down into the lungs and then pump it back out again and repeat, a neck longer than eight feet could mean suffocation. Weight is another problem. A water-dwelling dinosaur like the Plesiosaurus, which had a neck 23 feet long, had buoyancy to support it underwater, but sauropods were land dwelling animals. Worst of all, basic principles of mechanics state that it would be extremely difficult to support a head on the end of what is essentially a long lever.
A study published in the online journal PeerJ by Michael Taylor, a vertebrate paleontologist at the University of Bristol, and Mathew Wedel of the Western University of Health Sciences in Califronia, sheds some light on how sauropods managed such lengthy necks. They found that the dinosaurs’ bird-like bone structure made their long necks possible in a number of ways. Firstly, sauropods had up to nineteen vertebrae in their necks. By comparison, birds have between thirteen and twenty-five and no mammal has more than nine. Giraffes have seven.
Secondly, like birds, the neck bones of these dinosaurs were essentially hollow. Up to sixty percent of their bones were air. The small spaces inside a sauropod’s bones contained air sacs. In birds, these sacs function to store air from the lungs and release its oxygen to the blood, even when the lungs are busy exhaling. This means sauropods were more efficient breathers than most mammals.
Taylor and Wedel also found that the head of a sauropod was comparatively small and light, making it easier for a very long neck to support without the head drooping. Sauropods didn’t need large heads: they probably didn’t even chew their food. Their moutha would have been for collecting food only. The roughage it ate would have been processed whole in the sauropod’s enormous, slow digestive system. In fact, the sauropod’s portly middle might have helped with its neck. Unlike giraffes or ostriches, sauropods had four sturdy legs and a wide deep torso to balance out the leverage of its head and neck.
The necks of various Sauropods.
There are advantages to having long necks, if an animal can overcome the difficulties. Such long necks almost certainly helped sauropods find the massive amounts of food they would have needed to survive while expending minimal energy. They may have used their necks as giraffes do, to reach the tops of trees where other foragers couldn’t reach. Alternatively, they may have used their necks more like geese do, for grazing wide areas without having to lumber great distances. Long necks probably also came in useful for both attracting and fighting for mates.
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