New fossil analysis reveals dinosaur with 50-foot neck

A rendering of the sauropod known as Mamenchisaurus sinocanadorum, which had a 15 meter long neck. Credit: © Júlia d’Oliveira

With their long necks and formidable bodies, sauropod dinosaurs have captured people’s imaginations since the first relatively complete fossils were discovered in the United States in the late 1800s. The original specimen from which the Natural History Museum’s Dippy was cast was among these discoveries.

Now an international team led by Stony Brook University paleontologist Dr. Andrew J. Moore, and including Prof. Paul Barret, Merit Researcher, of London’s Natural History Museum, reported that a late Jurisprudence Chinese sauropod known as Mamenchisaurus sinocanadorum had a 50-foot (15-meter) long neck.

The revelation comes as part of a paper that aims to document the diversity and evolutionary history of the family Mamenchisauridae, a group of particularly long-necked sauropod dinosaurs that roamed East Asia and possibly other parts of the world from the Middle Jurassic to early times. Chalk (about 174-114 million years ago).

Lower jaw and two vertebrae fused together

The lower jaw and two of the vertebrae are connected to each other. Credit: Trustees of the Natural History Museum

Mamenchisaurus sinocanadorum was discovered in approximately 162-million-year-old rocks from the Xinjiang Uyghur Autonomous Region in northwest China in 1987 by the China-Canada Dinosaur Project team, after which it was named in 1993. Standing approximately 15.1 meters tall, its neck was more than six times longer than the neck of giraffes and 1.5 times the length of a double-decker bus! This makes it potentially the longest neck of any animal that has ever existed.

For sauropods, the long neck was one of the keys to achieving large body size. To power such a large body, sauropods had to be efficient at gathering food, and that’s exactly what a long neck was built for. A sauropod could stand in one place and graze the surrounding vegetation, conserving energy while consuming tons of food. Having a long neck probably also allowed sauropods to dissipate excess body heat by increasing their surface area, much like the ears of elephants. This lifestyle was exceptionally successful with the sauropod lineage appearing early in dinosaur evolutionary history and continuing until the last days of Mesozoicwhen an asteroid wiped out most dinosaurs, except relatives of modern birds.

Lower jaw and two vertebrae

The lower jaw and two of the vertebrae are connected to each other. Credit: Trustees of the Natural History Museum

The question of which sauropod had the longest neck is not easy to answer. The largest sauropods tend to be some of the least known, as it is very difficult to completely bury such a large animal in sediment, the first stage required for fossilization. Poor preservation of these specimens and their closest relatives often makes estimates of their neck length speculative.

Though Mamenchisaurus sinocanadorum known only from a handful of bones from the neck and skull, the research team was able to reconstruct its evolutionary relationships and thus make comparisons with the unusually complete skeletons of its closest relatives. This allowed them to conclude that Mamenchisaurus sinocanadorum had a neck of approx. 15.1 meters long, the longest of any known sauropod.

Lead author Dr. Andrew J. Moore, paleontologist at Stony Brook University, said: “All sauropods were large, but jaw-droppingly long necks didn’t just evolve once.

“Mamenchisaurids are important because they pushed the limits of 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 may be the record holder – at least until something longer is discovered.”

Paul Barrett studies the Mamenchisaurus sinocanadorum specimen

Prof Paul Barrett studies the Mamenchisaurus sinocanadorum specimen at the Paleozoological Museum of China in Beijing. Credit: Trustees of the Natural History Museum

The question of how sauropods managed to develop such long necks and large bodies without collapsing under their own weight has puzzled scientists since their discovery. When studying Mamenchisaurus the team was able to use computed tomography (CT) scanning to reveal that the vertebrae were light and hollow with air spaces making up about 69-77% of their volume, similar to the lightly built skeletons of birds. However, such featherweight skeletons would also be more prone to injury. To combat this Mamenchisaurus had 4-meter-long rod-like cervical ribs, bony extensions of the vertebrae that created overlapping bundles of rods on either side of the neck. These bundles would have stiffened the neck Mamenchisaurus sinocanadorumwhich increases its stability.

The remaining mystery of Mamenchisaurus and many other long-necked sauropods understand how they drew air down through those long necks all the way to their lungs.

Prof. Paul Barrett, Merit Researcher, Natural History Museum London explains, “Like all other sauropod dinosaurs, Mamenchisaurus had a complex respiratory apparatus that included not only the lungs but also numerous balloon-like air sacs. These were connected to the lungs and trachea, but spread through the interior of the animal’s throat, chest and abdomen.

“Taken in combination, these air sacs had a much larger volume than the lungs, and they even went into the bones and hollowed them out. This extra space would have helped these giant sauropods move the large amount of air in the long trachea that would have occupied their extraordinary necks.”

While Mamenchisaurus sinocanadorum now thought to have the longest neck of any dinosaur, it was still not the largest dinosaur. This title is held by a species in the titanosaur group and dinosaur fans get the chance to see the colossal titanosaur Patagonian swimmerone of the largest known creatures to ever walk our planet, this summer at London’s Natural History Museum.

Reference: “Reassessment of the Late Jurassic eusauropod Mamenchisaurus sinocanadorum Russell and Zheng, 1993, and the evolution of unusually long necks in mamenchisaurids” by Andrew J. Moore, Paul M. Barrett, Paul Upchurch, Chun-Chi Liao, Yong Ye, Baoqiao Hao, and Xing Xu, 15 March 2023, Journal of Systematic Paleontology.
DOI: 10.1080/14772019.2023.2171818

The new paper Reassessment of the Late Jurassic eusauropod Mamenchisaurus sinocanadorum Russell and Zheng, 1993, and the evolution of unusually long necks in mamenchisaurids is published in Journal of Systematic Paleontology. The research was funded by several organizations, including the United States National Science Foundation, The Royal Society of London and the National Natural Science Foundation of China.

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