Mei long was a small duck-sized dinosaur that lived about 130 million years ago. In Chinese, its name means "soundly sleeping dragon," a reference to the posture in which it was discovered: curled up with its head tucked under a forelimb. This posture is identical to that used by modern birds while dozing. Scientists think that birds sleep this way to keep warm, and the discovery of Mei long supports the theory that some dinosaurs were warm-blooded like modern birds.