Mei

Mei is an exquisite miniature troodontid theropod discovered in the Early Cretaceous beds of Liaoning, China. Measuring barely half a metre in total length, this duck-sized predator is internationally famous because its fossil was preserved in three dimensions while sleeping. The animal was found tucked into a circular ball, with its legs folded underneath its torso and its snout rested beneath an arm, identical to the roosting posture modern birds use to conserve warmth. Volcanic ash or suffocation likely entombed it instantaneously. Although soft feather impressions are scarce on the original specimen due to its three-dimensional volcanic preservation, closely related troodontids confirm it possessed a dense plumage. Mei likely preyed upon small lizards, mammals, and insects, hunting stealthily along the forest floor before curling up against the chill of the Jehol night.

The holotype fossil preserves the animal curled up in an avian roosting posture, with its head tucked under its wing.

Where and when

Mei lived in the Early Cretaceous, from 125.8 to 122.5 million years ago (Barremian-Aptian age). Its remains come from China, in the Yixian Formation.

The numbers

Length 0.5 m. Mass about 0.57 kg. Hip height about 0.2 m. That is 0.3 human-lengths, or 0.04 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, hip height.

Compare Mei with a bus Place on the timeline