Yunnanosaurus

Yunnanosaurus was a large herbivorous sauropodiform dinosaur from the Early to Middle Jurassic of southern China. Known from dozens of well-preserved skeletons discovered in Yunnan Province, it has provided palaeontologists with immense insights into the evolutionary transition toward true sauropods. Measuring roughly seven to eight metres in length and weighing over a tonne, Yunnanosaurus was substantially larger and more robust than most earlier prosauropods. Its dentition was particularly distinctive, featuring self-sharpening, spoon-shaped crowns with sixty or more closely set teeth in each jaw. These teeth wore down at an angle through regular mastication, functioning remarkably like the teeth of advanced sauropods rather than the serrated leaf-shaped teeth typical of basal prosauropods. While capable of quadrupedal posture during walking, its strong rear legs enabled it to stand upright to reach canopy foliage.

Its spoon-shaped teeth wore down like those of true sauropods, self-sharpening against opposing crowns.

Where and when

Yunnanosaurus lived in the Early Jurassic, from 201 to 168 million years ago (Hettangian-Bajocian age). Its remains come from China, in the Lufeng Formation.

The numbers

Length 7.5 m (estimates run from 7 to 8 m). Mass about 1.9 t. Hip height about 2 m. That is 4.4 human-lengths, or 0.67 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, first ma, last ma, hip height.

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