Limusaurus

Limusaurus is a small, slender ceratosaur discovered in the Late Jurassic rocks of Xinjiang, China. It is particularly renowned for dramatic changes during its growth. Juvenile specimens possessed sharp teeth, but as they matured, they lost all their teeth and developed a toothless beak instead. Preserved with polished gizzard stones inside their ribcages, adult specimens show clear evidence of shifting to an entirely plant-based diet. 7 metres long, Limusaurus had lightly built limbs suited for fast running. Its hands were uniquely reduced, bearing an extremely tiny first finger, which provided crucial evidence for how modern bird wings evolved from dinosaur hands. Many skeletons were discovered preserved together in prehistoric mud pits, where groups became trapped in quicksand created by volcanic ash.

Juveniles had teeth, but fully grown adults lost them entirely and relied on beaks and gizzard stones.

Where and when

Limusaurus lived in the Late Jurassic, from 161.5 to 158.7 million years ago (Oxfordian age). Its remains come from China, in the Shishugou Formation.

The numbers

Length 1.6 m (estimates run from 1.5 to 1.7 m). Mass about 19 kg. Hip height about 0.6 m. That is 0.9 human-lengths, or 0.14 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, hip height.

Compare Limusaurus with a bus Place on the timeline