Dino of the Week: Yunnanosaurus

Type Species: Yunnanosaurus youngi

Classification: Dinosauria - Saurischia - Prosauropoda

Time Period: Early to Middle Jurassic

Location: China

Diet: Herbivore

Yunnanosaurus lived in China during the Early to Middle Jurassic Period. Fossils from more than twenty different individuals have been found in the southern Chinese Yunnan Province (hence the creature’s name). Of these fossils, two include skulls, one complete with sixty teeth. Yunnanosaurus’ discovery – along with that of its contemporary Lufengosaurus – showed the worldwide distribution of sauropodomorphs by the Early Jurassic. 

Yunnanosaurus was a prosauropod that resembled earlier prosauropods such as Plateosaurus. It could grow up to twenty-three feet in length and – in the largest specimens – up to thirteen feet tall. It had a small head with a relatively short snout; a long neck and bulging body; sturdy legs with the rear pair slightly longer and stronger than the forelimbs; and a long, tapering tail. It was likely a gregarious herbivore that moved about in herds. These creatures would’ve spent most of their days plodding among the early Jurassic forests of conifers, cycads, and tree-ferns, feeding on soft leaves, shoots, and buds – and keeping a wary eye out for large theropod predators such as Sinosaurus and Shuangbaisaurus. Yunnanosaurus’ teeth were spoon-shaped and numbered more than sixty. The type of teeth makes it an oddball among prosauropods, most of which had leaf-shaped teeth. Though sauropods had spoon-shaped teeth, scientists doubt that Yunnanosaurus is a ‘missing link’ between prosauropods and sauropods, since Yunnanosaurus lacks any other ‘transitional features’: in anatomical build, except for the teeth, it’s a strict prosauropod. The spoon-shaped teeth, then, are viewed as a matter of convergent evolution, wherein Yunnanosaurus evolved spoon-shaped teeth to suit its environment and did so separately from sauropods.