Sauropods Held Their Heads High, Research Finds
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 worldwide.
Recent depictions such as the BBC’s Walking With Dinosaurs show them with their long necks held horizontal and their heads near the ground. But now scientists are saying the low-necked sauropod 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, and Dr Matt Wedel, of Western University of Health Sciences in California, 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 while the neck is only gently inclined in salamanders, turtles, lizards and crocodilians, it is vertical in mammals and birds – the only modern groups that share the upright leg posture of dinosaurs.
Dr Taylor said: “Like the animals we have with us today, they would have spent most of their time with their necks elevated, except when drinking or browsing at low levels.”
Modern vertebrates, from cats and humans to sauropods’ closest living relatives, the birds, hold their necks aloft in a vertical or near-vertical position.
Dr Wedel said: “We can’t just study fossil bones by themselves. 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.
Dr Taylor said: “Scientists have assumed that each pair of facets must maintain at least a 50 percent overlap at all times; but looking at what ostriches and giraffes do, we see that their facets can slide much further, until they hardly overlap at all. This means that sauropods would have had a far greater range of neck movement than has been thought in recent times.
“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 meant a graceful swan-like S-curve to the neck, and a look quite different from the recreations we are used to seeing today.”