Chungkingosaurus

Chapter • Meet the dinosaur

Overview

Chungkingosaurus was a small stegosaur from the Late Jurassic of what is now the Sichuan Basin in China. At roughly 3–4 metres long and a few hundred kilograms in most published estimates, it ranks among the smallest stegosaurs known. Its body was compact, the hind limbs clearly longer than the forelimbs, and the back arched so that the hips sat higher than the shoulders. Its most distinctive feature was the armour along the back: instead of the broad, thin plates of Stegosaurus, Chungkingosaurus carried thick, narrow plates that look like a halfway stage between a plate and a spike. Stout spikes were arranged near the end of the tail, and the skull was small, low and tipped with a horny beak. Like all stegosaurs, Chungkingosaurus walked on all fours and could not rear up to feed high in the trees. It browsed close to the ground, most likely on ferns, horsetails, cycads and other low-growing plants, and its small leaf-shaped teeth were suited to snipping soft plant material rather than grinding tough wood. Because the dentition was weak, many researchers think stegosaurs swallowed a great deal of poorly processed foliage and relied on a large gut for digestion. The tail spikes are usually interpreted as defensive weapons — the big predator Yangchuanosaurus is found in the same beds — while the function of the back plates remains debated, with display, species recognition and some degree of protection all proposed. The species was described in 1983 by the Chinese palaeontologists Dong Zhiming, Zhou Shiwu and Zhang Yihong, based on material from the upper part of the Shaximiao Formation at Jiangbei near Chongqing (formerly spelled Chungking); both the genus and species names refer to the discovery area. The holotype is an incomplete skeleton preserving parts of the skull, vertebrae, pelvis, limbs, plates and spikes, and additional individuals have since been referred to the genus. The position of Chungkingosaurus in the stegosaur family tree is contested. Some analyses place it near the base of Stegosauridae, while other workers have suggested that at least some of the material may represent juveniles of other Chinese stegosaurs such as Tuojiangosaurus. The question is unresolved, and modern redescriptions of the Chinese specimens are needed to settle it.

Chapter • Where it lived

Habitat

Chungkingosaurus lived about 161–155 million years ago, in the Late Jurassic, in what is now the Sichuan Basin of southern China. Its fossils come from the upper Shaximiao Formation at Jiangbei, Chongqing — a thick sequence of sandstones and mudstones laid down by braided rivers and across broad floodplains. The setting was warm with a seasonally wet climate, with stands of cycads, conifers and ginkgos, dense thickets of ferns and horsetails along the watercourses, and extensive lakes. The same rocks have yielded abundant remains of Mamenchisaurus, Omeisaurus, Tuojiangosaurus and Yangchuanosaurus, making the region one of the world's most important windows on Jurassic dinosaur life.

Chapter • Wild behavior

Behavior & Ecology

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Chapter • Scientific place

Taxonomy