Avimimus

Avimimus was a lightly built, bird-like theropod that lived during the Late Cretaceous in what is now the Gobi Desert of Mongolia and northern China. 5 metres long, this fleet-footed runner possessed exceptionally long, slender legs with fused lower leg bones akin to those of modern running birds. Its skull ended in a short, toothless, keratinous beak, suggesting an omnivorous diet composed of seeds, vegetation, and small insects. Notably, the ulna of its forearm bore tiny ridges interpreted as quill knobs, demonstrating that it carried broad feathers along its arms. Fossil bonebeds containing numerous individuals suggest that Avimimus congregated in flocks, moving rapidly across river plains and sand dunes while relying on keen eyesight and speed to escape larger predators.

Ulnar quill knobs provide direct fossil evidence that it bore pennaceous wing feathers.

Where and when

Avimimus lived in the Late Cretaceous, from 72 to 68 million years ago (Maastrichtian age). Its remains come from Mongolia and China, in the Nemegt Formation.

The numbers

Length 1.4 m (estimates run from 1.2 to 1.5 m). Mass about 17 kg. Hip height about 0.6 m. That is 0.8 human-lengths, or 0.13 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.

Compare Avimimus with a bus Place on the timeline