China fossil reveals giant dinosaur with neck longer than school bus

A close examination of the bones revealed that it had a 15.1 meter (49.5 foot) long neck — longer than a school bus. The beast weighed in at around 70 tonnes. They named the species Mamenchisaurus sinocanadorum, making it one of the top contenders in the sauropod clan — a group of dinosaurs with long necks.

“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 paleontologist Andrew J. Moore, as per the press release.

To estimate the neck size, the team also compared the remains with other related sauropods. The next longest-necked dinosaur after M. sinocanadorum is Xinjiangtitan shanshanesis (measuring 43.9 feet or 13.4 m).

The mysterious evolution of long necks 

Because of their enormous size, it is difficult to find well-preserved sauropod remains. As a result, little is known about this group of dinosaurs, particularly how they evolved to have long necks. And this continues to be a mystery.

However, they were able to learn some interesting facts about the species as a result of this study.

One major question that arose after claiming the length of its neck was how this species managed to live with such a long neck, and that too without falling under its own weight. To figure this out, the team conducted CT scans of the fossils to look for clues.

The researchers found that its vertebrae "were mostly air" — the creature had air-filled bones, similar to modern birds. Despite having lightweight bones, they were strong due to the presence of rod-like ribs that supported their neck. This feature gave them balance, increased stability, and protected the species from neck injuries. 

Moreover, this plant-eating dinosaur could have enjoyed large areas of surrounding vegetation from a single spot – thanks to the long neck.

This research advances our understanding of the mysterious sauropod clan. “Mamenchisaurus sinocanadorum underscores how much we can learn about sauropod evolution even from very incomplete specimens,” adds co-author Ye Yong, director of the Research Center of Jurassic Stratigraphy and Paleontology at the Zigong Dinosaur Museum in China’s Sichuan Province.

The findings were published in the Journal of Systematic Palaeontology.

Study abstract:

The sauropod genus Mamenchisaurus, from the Late Jurassic–Early Cretaceous of East Asia, has a convoluted taxonomic history. Although included in the first cladistic analysis of sauropods, only recently has the monophyly of Mamenchisaurus, and the anatomical diversity of the many penecontemporaneous East Asian eusauropods, been evaluated critically. Here, we re-describe the holotype and only specimen of M. sinocanadorum. Although the original diagnosis is no longer adequate, we identify several autapomorphies that support the validity of this species, including an elongate external mandibular fenestra and distinctive pneumatic structures on the cervical centra. We incorporate new data into a phylogenetic character matrix that also includes Bellusaurus and Daanosaurus, both of which are known only from juvenile material and are often hypothesized to be neosauropods (or close relatives thereof). We recover all species of Mamenchisaurus as part of a radiation of predominantly Middle–Late Jurassic East Asian eusauropods, but the genus is non-monophyletic, underscoring the need for further systematic revision of mamenchisaurid taxonomy. Analyses that score ontogenetically variable characters ambiguously recover Bellusaurus and Daanosaurus as juvenile mamenchisaurids, a hypothesis supported by several features that are unique to mamenchisaurids or exhibit little homoplasy, including anteriorly bifurcate cervical ribs. Finally, computed-tomography reveals extensive vertebral pneumaticity in M. sinocanadorum that is comparable to that of the largest sauropods, and updated scaling analyses imply a neck over 14 m long, rivalling estimates for other exceptionally long-necked sauropods.