Yinlong

Yinlong was a small, two-legged herbivore discovered in Late Jurassic deposits of the Shishugou Formation in Xinjiang, China. 2 metres in length, it was about the size of a medium dog and weighed around 10 to 15 kilograms. Described in 2006, Yinlong is exceptionally important to evolutionary biologists because it represents one of the oldest and most basal ceratopsians ever found. Despite having ancestral traits that resemble early ornithopods and pachycephalosaurs, its skull already featured the diagnostic rostral bone that defines the horned dinosaur lineage. One beautifully preserved skeleton even preserved polished gastroliths, or gizzard stones, in the stomach cavity. These stones helped grind tough vegetation, indicating that even early ceratopsians possessed specialized adaptations for processing coarse plant material.

It preserved gastroliths inside its ribcage, providing direct physical evidence for grinding plant matter.

Where and when

Yinlong lived in the Late Jurassic, from 161.5 to 157.3 million years ago (Oxfordian age). Its remains come from China, in the Shishugou Formation.

The numbers

Length 1.2 m. Mass about 12 kg. Hip height about 0.4 m. That is 0.7 human-lengths, or 0.11 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, hip height.

Compare Yinlong with a bus Place on the timeline