Dinosaur Tales

It

seems hard to believe, but it wasn't that long ago that the idea of birds evolving directly from dinosaurs seemed just a little flaky. Sure, they shared generally similar body plans — paleontologists have known that for more than a century — but that hardly constituted an airtight case. Over the past couple of decades, however, scientists have uncovered all sorts of detailed characteristics common to birds and dinosaurs: wishbones, swiveling wristbones and, most recently, proof that some dinosaurs sported feathers. There's behavioral evidence too. Some dinosaurs made nests and sat on them, and one four-winged, feathered dino evidently glided like a flying squirrel.

A flurry of new finds offers even more evidence that the pigeon you see in the park had an ancestor that ruled the earth. Writing in Nature over the past two weeks, Chinese and American paleontologists announced the discovery of one dinosaur that evidently slept curled up in a posture identical to that of a sleeping duck and another that is the first tyrannosaur ever found with feathers. The discovery of the tyrannosaur is significant because that family of dinosaurs is believed to be among the closest relatives of modern birds.

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Another team, meanwhile, recently published an analysis showing that Tyrannosaurus rex grew (and thus metabolized) at an impressively fast rate — suggesting that it might have been warm-blooded like birds. "There's now so much material [linking dinosaurs and birds] that I can't imagine anybody being able to ignore it," says paleontologist Luis Chiappe of the Natural History Museum of Los Angeles County.

Like many of the most dramatic dinosaur finds of the past few years, the new specimens were unearthed in a geological formation in northeastern China's Liaoning province that has become one of the world's most renowned fossil beds. Since the late 1990s, digs in Liaoning have produced an astonishing array of exquisitely preserved plants, insects, primitive mammals, birds and, most famously, feathered and winged dinosaurs.

Luckily for paleontologists, the beds are divided into different layers that yield different sorts of fossils. The sleeping dino, for example, was found in what Mark Norell of the American Museum of Natural History in New York City calls Liaoning's "Pompeii layer," a 10-ft.-thick stratum of ash and sand. It was deposited so quickly that, like the ash from the infamous eruption in Italy, it buried creatures alive wherever they were standing — or snoozing. This one was tiny: excluding its tail, it's about the size of a Rock Cornish hen. That some of its bones have not completely fused indicates that this particular specimen was not quite fully grown.

In 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.

"Not only are troodontids very closely related to birds," says Norell, "but this particular one is in a stereotypical resting pose of birds." The sleeping dragon was found sitting on its hindlimbs, its forelimbs folded at its side, its head tucked under its left elbow and its long tail curled around its body. Experts believe modern birds sleep in a similar position to conserve heat; presumably Mei long did too, which suggests that the animal was warm-blooded. If that was the case, says Norell, it also offers an explanation for feathers: "It's likely they first evolved for insulation rather than flight." Birds simply found another use for them.