June 22, 2009

Dinosaur fossil shows finger evolution

U.S. and Chinese scientists say their discovery of a beaked, plant-eating dinosaur fossil shows how birds' three-fingered claws evolved from dinosaurs.

The researchers said their finding also demonstrates theropod, or bird-footed, dinosaurs were more ecologically diverse in the Jurassic period than previously thought.

This new animal is fascinating, and when placed into an evolutionary context it offers intriguing evidence about how the hand of birds evolved, said Professor James Clark of George Washington University.

Clark, graduate student Jonah Choiniere and Xu Xing of the Chinese Academy of Science's Institute of Vertebrate Paleontology and Paleoanthropology in Beijing discovered the fossil of Limusaurus inextricabilis (mire lizard who could not escape) in 159 million-year-old deposits at the Junggar Basin of Xinjiang in northwestern China. The researchers said the dinosaur earned its name from the way its skeletons were preserved, stacked on top of each other in fossilized mire pits.

This finding is truly exciting, as it changes what we thought we knew about the dinosaur hand, Xu said. It also brings conciliation between the data from million-year-old bones and molecules of living birds.

The discovery was reported in the journal Nature.