‘Gargantuan’: China fossils reveal 70-tonne dinosaur had 15-metre neck

A dinosaur that roamed east Asia more than 160m years ago has been named a contender for the animal with the longest neck ever known.

A new analysis of bones from the beast’s neck and skull revealed that the dinosaur, known as Mamenchisaurus sinocanadorum, sported a neck 15metres long, or one-and-a-half times the length of a doubledecker bus.

The fossilised remains of the creature were recovered in 1987 from 162 million-year-old rocks in the Xinjiang Uyghur Autonomous Region of north-west China, but the full length of the animal’s neck was only recently reassessed by scientists.

The dinosaur was one of the huge herbivorous sauropods that grew to 50 metres from snout to tail and weighed more than 70 tonnes. Despite only a handful of bones remaining of the beast, researchers were able to estimate the length of its neck by comparing the remains with complete fossils belonging to closely related dinosaurs.

“Mamenchisaurus sinocanadorum might be the longest-necked sauropod discovered so far, but odds are that there were larger, longer sauropods roaming around the Late Jurassic of what is now China,” said Andrew Moore, a palaeontologist at Stony Brook University in New York.

“Unless we’re willing to believe that we just so happened to discover the largest single individual sauropod that ever existed, our default assumption should always be that there were larger animals out there. We can only hope that some of these titans fossilised, and are just waiting to be discovered by paleontologists.”

A long neck was one of the fundamental body features that allowed sauropods to reach such gigantic proportions. It allowed the animals to graze vast areas of vegetation while standing in one spot, meaning they could take in tonnes of food without expending much energy. Having a long neck may also have helped the animals to keep cool by increasing their surface area – a trick elephants achieve with their large ears.

The sauropods’ lifestyle was impressively successful, evolving early in dinosaur history and lasting until the final days of their reign during the mass extinction event triggered by an asteroid impact 66m years ago. The only dinosaurs that survived are the ancestors of modern birds.

How sauropods evolved such long necks and large bodies without collapsing under their own weight has puzzled scientists since the first fossils of the animals were recovered. But X-ray scans of the Mamenchisaurus fossils show that the vertebrae were light and hollow, with airspaces making up two-thirds to three-quarters of their volume. Similar skeletal features are seen in birds that minimise weight in order to fly. On sauropods, such lightweight skeletons would be prone to fracture, but the animal had rod-like neck ribs – bony extensions of the vertebrae – which stiffened the neck and improved its stability.

“One of the most remarkable facts about enormous sauropods is just how lightly constructed their bones could be,” Dr Moore said.

“Like their living cousins, birds, sauropods had a lung capable of invading bone and replacing heavy marrow and bone tissue with airspace. Such a lightweight build would have been critical to lightening the gargantuan necks of the largest sauropods.”

Details are published in the Journal of Systematic Palaeontology.