This Dinosaur’s Neck Was Longer Than A City Bus, New Calculations Show

Mamenchisaurus sinocanadorum had a neck around 15 metres long, which makes it the longest-necked dinosaur on record.

For context, the largest buses in most Indian cities are about 12-13 metres long, which means they are shorter than the 15-metre-long neck of the Mamenchisaurus sinocanadorum. It was a sauropod that roamed China about 160 million years ago.

Source : Julia d'Oliveira/Natural History Museum

Among dinosaurs, a sub-group called the sauropods are known for their extremely long necks. Now, calculations have shown that at least one of them had a neck around 15 metres long, which makes it the longest-necked dinosaur on record.

For context, the largest buses in most Indian cities are about 12-13 metres long, which means they are shorter than the 15-metre-long neck of the Mamenchisaurus sinocanadorum. The study has been published in the Journal of Systematic Palaeontology.

The dinosaur itself is not a new find. The only known specimen of Mamenchisaurus sinocanadorum was discovered in China in August 1987. But because it is not a complete specimen, the length of its length was not clear until now.

Mamenchisaurus sinocanadorum was a sauropod that roamed China about 160 million years ago, towards the later part of the Jurassic Period. Although its neck has now been shown to be the longest known, it is not the largest dinosaur ever discovered. Its tail and body were relatively short, so its overall length was smaller than that of some other sauropods.

How the length was calculated

The only existing specimen of Mamenchisaurus sinocanadorum is an incomplete skeleton that includes the front end of the neck, a rib and a few skull bones. 

To calculate the length of its neck, scientists wanted to compare it with another sauropod skeleton, which was better preserved. Although another Mamenchisaurus sinocanadorum specimen was not available, the skeleton of another kind of sauropod eventually made the comparison.

This giant sauropod, also found in China, is called Xinjiangtitan. Found in 2012, its skeleton had a complete neck. Scientists, therefore, compared the incomplete Mamenchisaurus sinocanadorum fossils with sauropods like Xinjiangtitan. Using what they described as “elementary maths”, they could work out what the neck length of Mamenchisaurus sinocanadorum would likely have been.

“So we measured the vertebrae in one dinosaur and the corresponding bone in the other and worked out the difference. We then multiplied the length of each vertebra that would have been present in a complete neck by that factor to get an estimate of the neck length in Mamenchisaurus sinocanadorum,” researcher Paul Barrett, a dinosaur expert, said in a statement released by the National History Museum, UK.

Why was its neck so long?

Scientists are trying to understand why Mamenchisaurus sinocanadorum had such a long neck. It is possible that the long neck made them easier to feed across longer distances while moving about less (this is also true of other sauropods), but the researchers believe the long neck also had other roles.

“It could have also been to do with sexual display or used for neck-butting contests between males fighting over mates and territory, similar to how giraffes behave today. But we can't say for sure. At this point, it's pure speculation as to why they evolved necks of this length,” the statement quoted Barr as saying.

The long neck, however, may also have curtailed the dinosaur’s other functions, so scientists are trying to work out how it managed to do things like holding up its neck, and even breathing.

“It would require a lot of muscles to hold up a neck that size, and then there's the question of how it gets air down to the lungs and back up again. This could support the theory that these necks were a sexually selected feature where only the strongest and fittest dinosaurs that were able to hold up these giant necks in impressive displays were able to mate,” Barrett was quoted as saying.