Description and Classification

Qijianglong was a large, four-legged herbivore, estimated to be around 15 meters (about 50 feet) in length. Like other sauropods, it had a long tail, a bulky body, and pillar-like legs to support its weight. Its most striking feature was its incredibly long neck, which likely measured about 7.5 meters (25 feet), making up roughly half of its total body length. The neck vertebrae (bones of the neck) were filled with air sacs, making them much lighter than solid bone. This adaptation helped Qijianglong support its long neck without it being too heavy.

Qijianglong belongs to the Mamenchisauridae family, a group of sauropod dinosaurs known for having some of the longest necks relative to their body size of any animal that has ever lived. These dinosaurs were common in Asia during the Jurassic period. Other mamenchisaurids include the famous Mamenchisaurus and Omeisaurus. The only known species is Qijianglong guokr. The species name “guokr” honors Guokr.com, a Chinese popular science website.

Distinguishing Features

Qijianglong possessed several characteristics that help set it apart from other sauropods, including its mamenchisaurid relatives:

• An exceptionally long neck, even compared to other mamenchisaurids, comprising about half its body length.
• Unique joints between its neck vertebrae. These bony connections suggest that its neck was relatively stiff when moving up and down but could bend and swing more easily from side to side. This structure would have provided support and stability for such a long neck.
• Lightweight neck vertebrae due to the presence of large air-filled cavities (pleurocoels), which reduced the overall weight of the neck.
• A relatively well-preserved skull found attached to the neck, which is rare for mamenchisaurids and provides valuable information about their head structure.

Paleoenvironment and Diet

Qijianglong lived in what is now southern China during the Late Jurassic epoch. The fossils were discovered in the Suining Formation. During this time, the region was likely a warm, moist environment with lush forests, rivers, and lakes. This rich ecosystem supported a variety of plant life, which formed the diet of herbivorous dinosaurs like Qijianglong. It would have shared its environment with other dinosaurs, potentially including other sauropods and theropod predators such as Yangchuanosaurus.

As a herbivore, Qijianglong used its extremely long neck to browse on vegetation. It could likely reach high into the tree canopy to feed on leaves, cones, and branches from tall plants like conifers, cycads, and Bennettitales, which were common during the Jurassic period. Its side-to-side neck flexibility might have allowed it to sweep a wide area for food without moving its entire body.

Significance and Ongoing Research

The discovery of Qijianglong is significant because it adds to our knowledge of the diversity and evolution of mamenchisaurid sauropods in Asia. The completeness of the neck and the attached skull are particularly important, as sauropod skulls are often delicate and rarely found with the rest of the skeleton. This find provides crucial anatomical details that help scientists understand the biology of these long-necked giants.

Ongoing research on Qijianglong continues to explore various aspects of its life. Scientists are studying the biomechanics of its neck to better understand how it moved and supported such an extreme structure. Further analysis of its fossils may clarify its exact evolutionary relationships with other mamenchisaurids like Mamenchisaurus and Chuanjiesaurus. Studying Qijianglong also helps paint a more complete picture of the Late Jurassic ecosystems of China and the role these enormous herbivores played within them.