Bird in the hand
Fossilized fingers strengthen evolutionary link between dinosaurs and avian relatives
By Sid Perkins
The hands of a newly discovered dinosaur species provide fresh support for the notion that birds are closely related to dinosaurs, researchers say.
Many paleontologists contend that theropods — a group of bipedal dinosaurs that, with rare exception, dined on meat — didn’t die out 65 million years ago with the rest of their kin. Analyses, those scientists say, show that this group lived on and gave rise to modern-day birds. But hardcore skeptics of that theory have long noted that the bone arrangement in birds’ wings doesn’t match the arrangement of bones in the hands of dinosaurs, says James M. Clark, a vertebrate paleontologist at George Washington University in Washington, D.C. Now, fossils of a new theropod species, described by Clark and his colleagues in the June 18 Nature, reveal that some theropods indeed had birdlike hand-bone arrangements.
The new species, an ostrich-sized dinosaur that lived in China about 159 million years ago, has been dubbed Limusaurus inextricabilis, the “mire lizard who could not escape.” Fossils of several of these creatures indicate that they became mired in a mudflat when its hard, thin crust gave way under their weight. Unlike most theropods, L. inextricabilis probably was a vegetarian: The species lacked teeth and had a beak. The clincher, Clark notes, is that some of the new fossils include gastroliths, or stomach stones — rocks swallowed to help grind vegetation and aid digestion.