Mamenchisaurus

About Mamenchisaurus

Features: The Secret of the Extremely Long Neck

The most prominent feature of Mamenchisaurus is its extremely long neck, which accounts for nearly half of its total length. In the case of Mamenchisaurus sinocanadorum, one of the largest species in Asia, the neck alone is estimated to have exceeded 15 meters, making it one of the longest of any animal on Earth.

To support such a long and heavy neck in the air, their bodies had incredible adaptations. The inside of the neck bones (cervical vertebrae) was hollowed out (pneumatized) like modern birds. It is thought that about 70% of the bone volume was filled with air, achieving significant weight reduction while maintaining physical strength.

In addition, elongated bones called "cervical ribs" extending beneath the neck bones overlapped with adjacent bones to form bundles, supporting the entire neck like the cables of a giant suspension bridge.

In the past, there was a time when it was thought that such a long neck evolved to eat leaves from high trees like a giraffe or to show off strength to peers (sexual selection). However, it is now known that the suspension bridge-like structure made it difficult for the neck joints to bend vertically.
Currently, it is believed that it was adapted to sweep its neck widely from side to side (like a vacuum cleaner horizontally) to eat low-lying plants such as ferns over a wide area without having to move its massive body.

The Hammer at the Tip of the Tail: "Tail Club"

It is known that at the tip of the tail of some Mamenchisaurus (such as the *hochuanensis* species), there was a small mass called a "tail club" formed by the fusion of several bones.

Although not as powerful as the giant hammers possessed by armored dinosaurs like Ankylosaurus, it seems to have had enough power to drive away carnivorous dinosaurs. In fact, a healed injury believed to be a strong blow from this tail club was found on the shoulder blade fossil of the large carnivorous dinosaur Yangchuanosaurus, which lived in the same era and region.

The "Wastebasket Taxon": Genus Mamenchisaurus

For many years, long-necked Jurassic dinosaurs found in Asia were temporarily classified as relatives of "Mamenchisaurus".

However, recent detailed research has revealed that the dinosaurs previously considered Mamenchisaurus do not belong to a single group (genus) evolved from a common ancestor, but are a mix of various types. Such a classification framework where similar things are temporarily thrown in is sometimes called a "wastebasket taxon" among researchers.

Currently, scientists are proceeding to organize this confused classification. A new concept called the "Core Mamenchisaurid-like Taxon (CMT)" has also been proposed, and in the future, the name "Mamenchisaurus" may be restricted to only a few species.

Why did Asian dinosaurs evolve so uniquely? During the Jurassic period, East Asia was like a giant island completely isolated from other continents by a shallow sea called the "Turgai Sea". Therefore, it is thought that sauropods such as Diplodocus and Brachiosaurus, which flourished in North America and elsewhere, could not enter Asia, allowing the Mamenchisaurus lineage to achieve unique gigantism and diversification.

Death Traps and the Environment of the Time

China, where Mamenchisaurus lived, had a different environment from the current inland Asia.

For example, a large number of dinosaur fossils have been found in the "Shaximiao Formation" in Sichuan Province. This area was an environment with lakes and marshes where giant rivers flowed in and rich forests spread, and it is known that they coexisted with various dinosaurs including stegosaurs.

On the other hand, the "Shishugou Formation" in Xinjiang Uygur Autonomous Region was a wetland dotted with active volcanoes. When a giant dinosaur weighing tens of tons like Mamenchisaurus walked around in the mud here, it created huge footprint holes 1 to 2 meters deep. Volcanic ash and muddy water flowed into them, making them look like extremely sticky swamps, which functioned as "death traps" where small dinosaurs mistakenly stepped in and could not escape.
In fact, the fossils of dinosaurs that died caught in these giant footprint traps have been found layered on top of each other.

History of Discovery and Origin of the Name

Mamenchisaurus was first discovered in 1952 at a highway construction site in Sichuan Province, China. The specific name "constructus" of the first named species, Mamenchisaurus constructus, comes from this "construction" work.

There is a slight episode regarding the origin of the genus name "Mamenchisaurus".
Dr. Chung Chien Young (Yang Zhongjian), a Chinese paleontologist who described this dinosaur in a paper in 1954, originally intended to name it after "Mamingxi (meaning a stream where horses neigh)", a ferry crossing where the fossil was found.
However, perhaps due to the doctor's strong accent or a mishearing during the reporting process, it was recorded as "Mamenxi (horse gate stream)", which was Latinized and registered as is.
Under the rules of international scientific names, once a name is formally registered, it cannot be corrected later even if it is a spelling error or a mishearing. Therefore, it continues to be called "Mamenchisaurus" to this day. If "Mamingxi" had been correctly adopted, it might have been called "Mamingxisaurus".

Mamenchisaurus Stamp and Fossil Gallery