The Sauropod Posture Debate, Part Eleventy
Did the long-necked sauropod dinosaurs hold their necks high in the air or low to the ground? If you think this is a question easily answered, you are sorely mistaken. In many ways sauropods were unlike any living creatures, and scientists have been debating their posture for years. Indeed, last month a short communication in Science suggested that the ancient giants held their heads low to the ground, but a new paper published in Acta Palaeontologica Polonica by Mike Taylor, Matt Wedel, and Darren Naish (who are also behind the SV-POW! blog) suggests that these dinosaurs regularly held their heads high.
A large part of the current debate has to do with the different ways of approaching the problem. You can study the bones of dinosaurs to get an idea of their posture, but they also would have required physiological mechanisms to do things like maintain blood pressure. A scientist who bases his or her hypothesis on skeletal anatomy may reach a very different conclusion than one who tries to reconstruct sauropod physiology. The authors of the new paper decided to look at the skeletal evidence and compared the necks of sauropods to many kinds of living vertebrates to see if the way living animals hold their necks could answer some questions about sauropods.
When they looked at the neck posture of birds, rabbits, cats, rodents, and primates, the team found that these animals typically held their necks vertically and that the middle part of the neck was relatively rigid. They also found that the living animals often had more flexibility in their necks than you would think just looking at bones alone. More striking, though, was that the animals studied, including the closest living relatives to dinosaurs (birds and crocodylians), held their necks up, not down. If almost all other land-dwelling vertebrates were doing it, there is a good chance sauropods were doing it, too. From what they found, the scientists strongly suggest that not only did sauropods hold their necks above a horizontal position, but they had a much wider range of motion than other scientists have suggested.
I have no doubt that the posture of sauropods will continue to be debated, especially in terms of physiology and feeding, but this paper is a very important contribution to the discussion. As the authors state, unless they were unlike almost all groups of terrestrial vertebrates, sauropods were "holding their heads high." For more be sure to check out the summaries of the paper at Tetrapod Zoology and SV-POW!, written by some of the authors of the study.