Mamenchisaurus hochuanensis

Chapter • Meet the dinosaur

Overview

Mamenchisaurus hochuanensis is one of the most extreme long-necked dinosaurs ever found. The animal reached roughly 20–22 metres in length, and almost half of that was neck alone. Its nineteen cervical vertebrae were elongated, thin-walled and riddled with air spaces, exactly as in modern birds, which made the huge neck surprisingly light. Long, overlapping cervical ribs ran backwards like splints, bracing the neck and making it stiff but strong. The head at the far end was small compared with the body, with spatulate teeth concentrated near the front of the jaws. The torso was compact and barrel-shaped, the limbs were pillar-like, and the tail long and tapering. In the original description, several thickened tail vertebrae were interpreted as a club-like structure at the tip. Like all sauropods, Mamenchisaurus walked on four legs with a level, horizontal posture and carried its tail clear of the ground – never dragging it. The long neck most likely worked as a feeding boom: standing still, the animal could sweep its head through a wide arc and strip a large area of vegetation, saving far more energy than moving its multi-tonne body. Researchers still debate how high the neck could be raised; the stiffened construction suggests it was usually held at a low to moderate angle rather than vertically like a giraffe. The diet was entirely plant-based: conifer foliage, ginkgo leaves, ferns, seed ferns and cycad-like plants. The teeth cropped rather than chewed, so food was broken down slowly in an enormous gut. An adult probably needed hundreds of kilograms of plant matter every day, and like other sauropods it grew extremely fast during its first decades before growth slowed in adulthood. The genus Mamenchisaurus was named after a find at a ferry crossing in Sichuan, China, in the 1950s. The species hochuanensis was described in 1972 by the Chinese palaeontologists Yang Zhongjian (Young Chung-Chien) and Zhao Xijin, based on material from Hechuan in the Chongqing region. The fossils come from the Upper Shaximiao Formation and rank among the most complete long-necked sauropods known from Asia. Mounted skeletons of the species are displayed in Chinese museums, and casts stand in exhibitions around the world.

Chapter • Where it lived

Habitat

Mamenchisaurus hochuanensis lived in the Late Jurassic, roughly 160–145 million years ago, in what is now Sichuan and Chongqing in southern China. Its fossils come from the Upper Shaximiao Formation, sediments laid down on broad floodplains crossed by meandering rivers, lakes and wetlands. The climate was warm with a seasonally wet rhythm, and the landscape was covered by conifer forests, ginkgo trees, tree ferns and dense ground vegetation – but no modern flowering plants yet. The same environment supported other sauropods such as Omeisaurus, the spiky stegosaur Tuojiangosaurus and the large predator Yangchuanosaurus.

Chapter • Family life

Breeding

Chapter • Wild behavior

Behavior & Ecology

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Chapter • Scientific place

Taxonomy