Tuesday, December 8, 2009

4 Winged Dinosaur


A Nova PBS Documentary Video

2002; Paleontologists in China discovered the fossil remains of a four- winged dinosaur with fully developed, modern feathers on both the forelimbs and hind limbs.
The new species, Microraptor gui, provides yet more evidence that birds evolved from dinosaurs, and could go a long way to answering a question scientists have puzzled over for close to 100 years: How did a group of ground-dwelling flightless dinosaurs evolve to a feathered animal capable of flying?
Xu Xing, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China, and colleagues suggest in the January 23 issue of the journal Nature that the species is an early ancestor of birds that probably used its feathered limbs, along with a long, feather-fringed tail, to glide from tree to tree. They argue that the animal represents an intermediate stage in the evolution of flight, from gliding much as flying squirrels do today to the active wing flapping of modern birds.

Xu's work has long been supported by the National Geographic Society's Committee for Research and Exploration.The six specimens were excavated from the rich fossil beds of Liaoning Province in northeastern China. They are dated at between 128 to 124 million years old (Early Cretaceous).

In 2002, the discovery of this beautiful and bizarre fossil astonished scientists and reignited the debate over the origin of flight. With four wings and superbly preserved feathers, the 130 million-year-old creature was like nothing paleontologists had ever seen before. In this program, NOVA travels to the Chinese stone quarry where the fossil was discovered (a famed fossil treasure trove) and teams up with the world’s leading figures in paleontology, biomechanics, aerodynamics, animation, and scientific reconstruction to perform an unorthodox experiment: a wind tunnel flight test of a scientific replica of the ancient oddity. Dubbed Microraptor, the crow-sized fossil is one of the smallest dinosaurs ever found and one of the most controversial, challenging conventional theories and assumptions about the evolution of flight. But how did Microraptor use its wings? Did it array its arm- and leg-mounted wings in the style of an early 20th-century biplane to produce high lift at low speed? Did it use them to create a single lifting surface for efficient, swift gliding? Did it employ some combination of these two methods? Or were the extra wings useless for flight and likely to have been for some other purpose, such as attracting a mate?

To answer these questions, NOVA interviews Chinese paleontologist Xu Xing, who first recognized the importance of Microraptor and gave it its name; paleontologist Mark Norell and artist Mick Ellison of the American Museum of Natural History; paleontologist Larry Martin of the University of Kansas; anatomist Farish Jenkins of the Museum of Comparative Zoology at Harvard University; and aerodynamicist Kenny Breuer of Brown University. In addition, NOVA commissions a “flight-ready” wind tunnel model of Microraptor complete with feathers and articulating joints. Artists have historically played an important role in paleontology by helping to reconstruct the appearance and behavior of ancient animals. In the case of Microraptor, two completely different reconstructions were made, one at the American Museum of Natural History, and the other at the University of Kansas, based on different specimens and different techniques. The two markedly different reconstructions play into a long-running scientific controversy over the origin of flight in birds. For years the debate has been a standoff between two camps—those who believe dinosaurs were the ancestors of birds, and those who do not.

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