Mamenchisaurus

Mamenchisaurus is a genus of Chinese sauropod famous for having the longest neck of any known animal. In some species, the neck makes up nearly half of the total body length. They possessed 18 or 19 cervical vertebrae, significantly more than the 15 found in Diplodocus or the 13–14 in brachiosaurids. The largest known species, M. sinocanadorum, had a neck estimated at 14–15 m, a record for any animal in Earth's history.

The dinosaur's body was built to support its extreme neck. Rod-like cervical ribs ran along multiple vertebrae to provide rigidity, allowing the animal to hold its neck out at horizontal or mid-level elevations. It had a deep but slender torso, columnar limbs, and a long tail. Despite their distance on the evolutionary tree, Mamenchisaurus had small skulls with peg-like teeth at the front of the jaw, an arrangement similar to that of diplodocids.

Several species have been named, though their validity is often debated. These include M. constructus, M. hochuanensis, M. anyuensis (the most recent species, surviving into the Early Cretaceous), M. sinocanadorum, M. youngi, and M. jingyanensis. Phylogenetically, the genus is part of the East Asian Mamenchisauridae, a lineage of basal eusauropods that diverged before the split between diplodocids and macronarians.

A 2023 study by Moore et al. used biomechanical modelling to revise neck estimates for M. sinocanadorum. They found that individual cervical vertebrae could reach 2.5 m in length, suggesting a total neck length approaching 15 m.

Its exceptionally long neck allowed Mamenchisaurus to sweep across a wide area to feed without needing to move its massive body. This strategy made grazing highly efficient. The cervical ribs provided the necessary structural support to hold the neck steady, while heavily pneumatised (air-filled) vertebrae reduced the weight of the structure. Fossil bonebeds and trackways indicate that these dinosaurs lived in herds. In the Late Jurassic of Asia, Mamenchisaurus coexisted with the stegosaur Tuojiangosaurus and several species of theropods.

• M. hochuanensis — Zigong Dinosaur Museum, Sichuan; spectacular full mount.
• M. sinocanadorum type material — neck vertebrae, IVPP V14661.
• M. constructus holotype (IVPP V790) — Institute of Vertebrate Paleontology, Beijing.

Maximum neck length — M. sinocanadorum may have had the longest neck of any animal ever, plausibly approaching 15 m (Moore et al. 2023). Species validity — multiple named species, taxonomy unsettled. Neck posture — biomechanical modelling supports gentle-elevation horizontal-to-mid posture rather than full vertical.

Mamenchisaurus is a fixture of Chinese dinosaur exhibitions and increasingly featured in international media. The Zigong mount is one of the most-photographed sauropod skeletons in the world. Prehistoric Planet (2023, Season 2) presents it as a long-necked feeder.

• sauropodomorpha
• diplodocus
• tuojiangosaurus

• Young, C.-C., & Zhao, X.-J. (1972). Mamenchisaurus hochuanensis sp. nov. Institute of Vertebrate Paleontology and Paleoanthropology Monograph A, 8, 1–30.
• Moore, A. J., et al. (2023). Re-assessment of the longest known neck and reconstruction of the body of Mamenchisaurus sinocanadorum. Journal of Systematic Palaeontology, 21, 2196966.
• Wedel, M. J. (2003). Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs. Paleobiology, 29, 243–255.
• Russell, D. A., & Zheng, Z. (1993). A large mamenchisaurid from the Junggar Basin, Xinjiang, People's Republic of China. Canadian Journal of Earth Sciences, 30, 2082–2095.