Jurassic dinosaur Mamenchisaurus sinocanadorum had nearly 50-foot neck, study finds

Imagine what a dinosaur could do with a neck almost 50 feet long — eight times longer than a giraffe’s.

The latest estimate of the neck length of a late Jurassic period dinosaur found in China — a Mamenchisaurus sinocanadorum — is nearly 20 feet longer than previous estimates for members of the sauropod family, according to Stony Brook University paleontologist Andrew J. Moore, one of the authors of an article on the creatures published Wednesday in the Journal of Systematic Palaeontology. 

At least these enormities evidently only ate plants.    

Only discovered in 1987, this specimen probably ate a few tons of shrubs, ferns and trees every day.

“Those animals that have the most efficiently built neck are going to be that much more competitive among their peers, and therefore more likely to survive and pass their genes on,” Moore said.

The animals were probably only able to lift their heads a shallow 20 to 30 degrees, and “the extreme length of the neck would still mean that the animal’s head could reach heights” of 8 to 11 yards, another of the article's authors, Paul Upchurch, a palaeobiology professor at University College London, said in a joint statement.

During the pandemic, researchers scrutinized previously found fossils of different types of sauropods — which roamed northwest China — with scans and modeling software, Moore said.

“It’s a long-term project to figure out how these lines were related to each other, how their long necks evolved; we have a lot of skeletons with different body sizes, so we can look at what’s changing to accommodate the body size increase.”

As to whether there were ever other dinosaurs with longer necks, Moore said, “The upper limit is almost certainly greater than 15 meters [nearly 50 feet] but remains unknown because of the paucity of such large specimens.”

Despite that super long neck, “Balance was likely not an issue,” Hans Larsson, an associate professor at McGill University and curator of vertebrate palaeontology at the Montreal school's Redpath Museum, said by email.

The sauropod was “gigantic with nearly straight, pillar-like limbs,” with huge bodies, “housing large digestive tracts.”

Tails were counterweights. Said Moore: “It’s not hard to imagine that having a nice, long tail could be a [sufficient] piece of ballast for having a long neck on the other end of the body.” 

Sauropods, along with other dinosaurs, have at least a few advantages over mammals. 

“They actually have pretty small heads,” said Moore, “unlike a mammal, whose head tends to get larger and heavier as that animal gets larger, investing the head with all those chewing muscles.” After all, who needs them?

“They didn’t really bother to chew their food — they stripped the leaves from plants and trees and swallowed them en masse.”

The species’ biomechanical wizardry far surpasses mere balancing acts.

Much like storks with “lightly built skeletons,” the dinosaurs had 69% to 77% of their vertebrae filled with air, the study found.

Yet dinosaur versions of Elizabethan collars were actually effective supports.

“Mamenchisaurus sinocanadorum had 4-meter-long [13-foot-long] rodlike cervical ribs, bony extensions of the vertebrae that created overlapping bundles of rods on either side of the neck,” which stiffened and stabilized it, the study said.

Larsson likened it to “a hollowed-out I-beam with internal struts." This configuration is not only light, but also keeps a high degree of mechanical strength.”

Like elephants, sauropods' vast appetites mean they probably ranged widely, Eric K. Lund, DinoLab manager at the North Carolina Museum of Natural Sciences, said by email.

And Earth was quite different 162 million years ago. “The environment was also warmer, more verdant, more vegetated. They probably could travel great distances foraging for low-quality food, spending lots of time in one spot eating then moving on to another patch of forest,” Lund said.

But they probably took their time.

“Modern giraffes are quite fast for their seemingly strange body form.  They can gallop up to 37 mph, while other studies suggest that sauropods, generally not this animal specifically, were only able to attain speeds of [about] 4 mph,” Lund said.

In addition to filling out the sauropod family tree, the research “also gives insights into the upper limits of these gigantic animals,” he added.