June 8, 2010
How high did the sauropod dinosaurs hold their heads? It is a simple question, but for years it has been part of an ongoing controversy about the evolution and habits of these long-necked, large-bodied vegetarians. Depending on whom you ask, sauropods either kept their heads down to vacuum up low-lying vegetation from a wide area or held them aloft to pluck foliage from a greater vertical range. A new study by Andreas Christian in Biology Letters suggests that at least a few sauropods held their heads high.
Euhelopus zdanskyi is hardly a household name, but Christian selected this dinosaur because its neck has specific characteristics which provide clues as to its posture. Overall Euhelopus would have looked like Brachiosaurus or Giraffatitan in form—a compact body with long forelimbs, a short tail and a very long neck. Christian used well-preserved vertebrae from the University of Uppsala, Sweden, to create a virtual reconstruction of the Euhelopus neck on which physical stresses and strains could be tested—and found that the neck that was not very flexible and that it would not have been held straight up or straight ahead. Instead, he concluded, Euhelopus probably held its neck the way giraffes do today—typically at an angle in front of the body.
Christian’s conclusions suggest that the necks of Euhelopus and similarly proportioned dinosaurs were adapted for browsing at a range of vertical levels, and that these large-bodied animals would have saved energy by standing in one place, browsing among high trees, rather than shuffling about in search of low-lying food. If this is correct, it may help explain why different sauropods lived beside one another; some may have browsed in the trees while others specialized in lower-lying food, reducing competition. It would have cost these dinosaurs a lot of energy to raise their heads, but not as much as walking over a larger area in search of lower-lying food. And as Christian concludes, “During a food shortage, raising the neck was probably even essential for surviving: it is better to get little than nothing at all.” While the posture and habits of other sauropod dinosaurs, such as the famous Diplodocus and Apatosaurus, are still being hotly debated, it seems that dinosaurs like Euhelopus kept their heads in the trees.
Christian, A. (2010). Some sauropods raised their necks–evidence for high browsing in Euhelopus zdanskyi Biology Letters DOI: 10.1098/rsbl.2010.0359
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