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...addition, it's a new species, which Norell and co-discoverer Xing Xu of Beijing's Institute of Vertebrate Paleontology and Paleoanthropology named Mei long, from the Chinese for "soundly sleeping dragon." But the specimen, dating to between 128 million and 139 million years ago, is clearly an early troodontid, an evolutionary cousin of tyrannosaurs...
...natural body postures, it was too coarse to take imprints of soft tissues and delicate structures, so there's no way of knowing whether Mei long had feathers. But other strata of the Liaoning fossil beds are much finer grained. That's where paleontologists found the feathered tyrannosaur, which Xu and Norell named Dilong paradoxus ("surprising emperor dragon"). It's one of the oldest known tyrannosaurs, and one of the emu-size specimens has unmistakable traces of primitive feathers on its tail and jaw. Those filaments, which are about three-quarters of an inch long and branched like modern feathers...
...supports the idea of warm-bloodedness, which means baby T. rex had to have a way to retain body heat. As the dinosaur shot toward adulthood, however, it would have developed the opposite problem: shedding the excess heat pumped out by an active, 11,000-lb. body. Norell and Xu theorize that T. rex probably lost its feathers as it matured, just as growing elephants lose their body hair...
...Staff writer Risheng Xu can be reached at xu4@fas.harvard.edu
...Staff writer Risheng Xu can be reached at xu4@fas.harvard.edu...