Mamenchisaurus hochuanensis

Mamenchisaurus hochuanensis was a very long-necked sauropod from the Upper Shaximiao Formation of southwestern China. Its holotype preserves an almost continuous articulated vertebral column and much of the limbs and girdles, making it far more informative than the fragmentary type species of Mamenchisaurus. The neck alone approached half the animal's total length. Although traditionally placed in the same genus, modern analyses warn that Mamenchisaurus has accumulated several anatomically different species and may require revision; M. hochuanensis nevertheless remains a well-defined and exceptionally complete animal in its own right.

Its fossils occur between approximately 159 and 150 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

Holotype CCG V 20401 is a nearly complete skeleton lacking the skull and some extremities. Young and Zhao counted 19 elongated cervical vertebrae and estimated a neck about 9.3 to 9.5 metres long, although later researchers have questioned whether the final element should instead be the first dorsal vertebra. Air spaces lightened the neck bones, while extremely long overlapping cervical ribs helped brace the neck. The torso was compact beside the neck, the limbs were columnar, and the tail ended in four fused vertebrae with expanded arches that have often been called a small tail club.

• Neck approximately 9.3–9.5 metres long
• Traditionally counted series of 19 cervical vertebrae
• Pneumatic recesses lightening the cervical vertebrae
• Extremely long overlapping cervical ribs
• Columnar limbs supporting a massive quadrupedal body
• Four fused terminal tail vertebrae with expanded neural arches

Local people had noticed bones on a slope above the Fu River near Taihe village in Hechuan, but they remained exposed until a Sichuan Provincial Museum team began excavation in 1957. Preparation and mounting were completed in 1965. C. C. Young and Xijin Zhao formally named Mamenchisaurus hochuanensis in 1972, using the older spelling Hochuan for today's Hechuan District. Additional material from the Upper Shaximiao Formation near Zigong includes another nearly complete skeleton and has helped test the anatomy seen in the holotype.

Discovery credit: Sichuan Provincial Museum field team.

Naming authors: C. C. Young, Xijin Zhao.

The Upper Shaximiao Formation records river channels, floodplains and lakes within the Sichuan Basin. Seasonal rainfall crossed a warm landscape supporting conifers, cycads, ferns and other plants. The wider formation preserves a diverse dinosaur fauna including other sauropods, stegosaurs and large theropods, but its long depositional interval means the named animals were not necessarily all neighbours at one moment.

Mamenchisaurus was a plant eater that could sweep a small head through a broad feeding envelope without moving its enormous body each time. The habitual height and flexibility of the neck remain debated; the bones do not support a single rigid giraffe-like pose or a permanently horizontal one. The fused tail tip may have served in defence, but it has also been discussed as pathology or a structure with another function. No direct evidence establishes herd size, parental care or mating displays for this species.

• Its neck was about as long as a city bus and approached half of the total body length.
• The holotype preserves nearly the entire vertebral column but no original skull.
• The famous count of 19 neck vertebrae may be one too many if the final element is actually the first back vertebra.
• Its four fused tail-tip vertebrae evolved independently of the much larger clubs of ankylosaurs.

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1. 01
   Mamenchisaurus hochuanensis sp. nov.

   C. C. Young, Xijin Zhao · Institute of Vertebrate Paleontology and Paleoanthropology Monograph Series I, No. 8 · 1972

   Open source
2. 02
   Why sauropods had long necks; and why giraffes have short necks

   Michael P. Taylor, Mathew J. Wedel · PeerJ 1 · 2013

   Open source
3. 03
   Surprisingly young age for the mamenchisaurid sauropods in South China

   Jun Wang, Mark A. Norell, Rui Pei and 2 coauthors · Cretaceous Research 104 · 2019

   Open source
4. 04
   Mamenchisaurus

   Fukui Prefectural Dinosaur Museum

   Open source