(CNN) – A plant-eating sauropod that lumbered around what’s now China some 162 million years ago had a neck that was about 10 feet longer than a typical school bus – and the longest of any known dinosaur.
The creature’s 49.5-foot-long (15.1-meter) neck would have allowed it to stand in one spot and hoover up the surrounding vegetation – maximizing the amount of food it consumed while conserving energy.
The fossilized remains of the dinosaur, called Mamenchisaurus sinocanadorum, were discovered in 1987 in China’s northwestern region of Xinjiang and first described in a 1993 scientific paper. The dinosaur was named after the joint Chinese-Canadian team that unearthed the fossil.
In a fresh analysis of the fossil published in the Journal of Systematic Palaeontology on Wednesday, paleontologists used computerized topography scanning that wasn’t widely available three decades ago to compare M. sinocanadorum with other related sauropods unearthedin recent years.
“Mamenchisaurids are important because they pushed the limits on how long a neck can be, and were the first lineage of sauropods to do so. With a 15-meter-long neck, it looks like Mamenchisaurus sinocanadorum might be a record-holder – at least until something longer is discovered,” said studylead author Andrew Moore, a paleontologist and assistant professor at New York's Stony Brook University in a statement.
The paleontologists were able to infer the length of the neck by studying the specimen’s three preserved vertebrae and comparing them with the neck bones of closely related dinosaurs.
“We actually happen to know who it is related to, which provides nice comparisons. In this case, it’s well nested evolutionarily within a lineage that we know had 18 cervical (neck) vertebrae,” Moore explained. “We can scale up from the comparators to figure out absolute neck length.”
The longest complete neck documented by scientists belongs to a fossilized dinosaur called Xinjiangtitan, Moore said, and that was about 5 feet (1.5 meters) shorter than the neck of M. sinocanadorum.
Hollow bones lighten the load
The study also revealed intriguing details about these massive dinosaurs. Similar to a bird's lightweight skeleton, M. sinocanadorum's bones were filled with air, rather than marrow, which is a characteristic of most mammal bones. CT scans showed that air made up 69% to 77% of the vertebrae's volume.
“Presumably, that’s an important mechanism for building such a long neck because that's going to get quite heavy,” Moore said.
While the posture of some sauropod species might have featured a neck held erect in swanlike fashion, Moore said that biomechanical studies suggested the Mamenchisaurid neck was elevated at an angle of about 20 to 30 degrees above the horizontal.
However, even at this relatively shallow angle, the neck’s extreme length would still mean the animal’s head could reach heights of around 24.6 to 32.8 feet (7.5 meters to 10 meters) above the ground.
The sauropod’s evolutionary adaptations – gigantic size and vegetarian diet – have no modern equivalent, according to the study. But the lineage of these long-necked dinos was very successful, with different sauropod species appearing early on in the dinosaur era and thriving until their extinction 66 million years ago.
“They’re seemingly well engineered to be efficient food gatherers and that’s what the neck allows them to do ... plant themselves in one space, eat the vegetation that's around them and then move only as necessary.
“As for why Mamenchisaurus among sauropods had relatively even longer necks? Maybe it’s just that much more efficient. ... It’s hard to say but it’s clearly something central to their biology.”
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