Chinese and US scientists reported in the Nature magazine published on October 14, 2004, their new prize unearthed at the Beipiao City, Liaoning Province: a fossilized dinosaur in sleeping posture, a first-ever look at how the prehistoric creatures slept..

XU Xing, a research fellow of the Institute of Vertebrate Paleontology and Paleoanthropology, a part of the Chinese Academy of Science, and his colleague Mark Norell, of the American Museum of Natural History in New York, believe that the perfectly preserved remains belong to a 140 million-year-old new species of dinosaur. The dinosaur was found curled up with its head tucked under the forearm similar to how modern birds sleep. XU and his collaborator wrote: "this is the first report of sleeping behavior in dinosaurs," and dubbed it Mei Long, meaning "a soundly sleeping dragon" in Chinese.

The dinosaur was about 53 cm long, or about the size of a large bird. Its sleeping posture indicates the characteristics probably originated in dinosaur ancestors of modern birds, according to the scientists. Several features also indicate that two animals may originate from the same ancestor, and their flying capability can be an evolutionary result of becoming lighter in weight. Scientists believe that the newly discovered dinosaur is a warm blood animal for its avian origins.