POMONA, Calif. – 05/27/2009 — Famous depictions of the largest of all known dinosaurs, from film and television to museum skeletons, have almost certainly got it wrong, according to new research.
Sauropods are the most iconic of prehistoric creatures. They were up to 30 metres long, weighed as much as 10 elephants, and are instantly recognisable by their very long necks and small heads. They are the centrepieces in most natural history museums.
Recent depictions such as the BBC’s Walking With Dinosaurs show sauropods with their necks horizontal and their heads near the ground. But now scientists say the low-necked pose is a mistake: new evidence indicates that they held their necks aloft like giraffes and all other living land vertebrates, making them up to 15 metres tall.
Dr. Mike Taylor and Dr. Darren Naish, of the University of Portsmouth, UK, and Dr. Matt Wedel, of Western University of Health Sciences in Pomona, Calif., argue that while sauropods could hold their necks low, it was not their habitual posture.
They studied X-rays of members of 10 different vertebrate groups and found that the neck is gently inclined in salamanders, turtles, lizards and crocodilians, it nearly vertical in mammals and birds – the only modern groups that share the upright leg posture of dinosaurs.
“”Like the animals with us today, they would have spent most of their time with their necks elevated, except when drinking or browsing at low levels,”” Dr. Taylor said.
Modern vertebrates, from cats and humans to sauropods’ closest living relatives, the birds, hold their necks aloft in a vertical or near-vertical position.
“”We can’t just study fossil bones by themselves,”” Dr. Wedel said. “”Dinosaurs were living animals and to understand how they lived, we need to look at animals that are alive today. In this case, our evidence shows the present is the key to the past.””
The neck vertebrae of sauropods fit together mainly by way of ball and socket joints. In addition, the top part of each vertebra has a pair of facets, two at the front and two at the back, which glide past each other when the neck bends.
“”Scientists have assumed that each pair of facets must overlap by at least 50 percent at all times; but in ostriches and giraffes the facets can slide much further, until they hardly overlap at all,”” Dr. Taylor said. “”This means that sauropods would have had a far greater range of neck movement than previously thought.
“”Unless sauropods carried their heads and necks differently from every living vertebrate, we have to assume that the base of their neck was curved strongly upwards. In some sauropods this would have given the neck a graceful swan-like S-curve, which would look quite different from the recreations we are used to seeing.””
Low necked poses for sauropods have been used for countless plastic toys and have become part of mainstream culture, thanks in part to the BBC’s Walking with Dinosaurs, and to new museum exhibits such as one at the American Museum of Natural History in New York.
“”It’s hugely important to understand how sauropod dinosaurs functioned,”” said Professor Mike Benton at Bristol University’s Department of Earth Sciences. “”They were so huge – 10 times the size of an elephant – and yet they were successful animals. This new work provides plausible evidence that sauropods held their necks elevated, rather than horizontally, as had been assumed.
“”The new work is based on studies of living animals, but the next step will be to carry out engineering studies to see whether the new or old neck positions are energetically more efficient. If you have a long neck that weighs a tonne or more you must hold it in a neutral position where stresses and strains are minimised.””
The research was published in Acta Palaeontologica Polonica and will be available for download beginning May 27 at http://www.app.pan.pl
– Artist’s impression of a sauropod herd with the correct neck posture. Please credit: Mark Witton
– A correct (neck aloft) reconstruction of the sauropod Brachiosaurus in the Humboldt Museum f