Wednesday, February 18, 2009

Birds and Dinsaurs

Nova, the science show on PBS, turned its attention to birds this week, in The Four-Winged Dinosaur, One of the issues they are exploring is the development of flight in birds.

Scientists debate two theories: that animals, dinosaurs, developed flight from the ground up, and that they developed it from the trees down, by gliding. New fossils from China add evidence to the discussion. These feathered dinosaurs, 130 million years old, were preserved with feathers and skin by volcanic ash, giving us previously unknown information about them. The show makes the point that the film Jurassic Park should have had feathers on Velociraptor. This reconstruction shows what Microraptor might have looked like.

Paleontologists are debating where this critter belongs in the evolution of birds: was it an ancestor of today’s birds, or was it a development that died out? Most scientists agree that contemporary birds are descendants of dinosaurs. Exactly where these feathered dinosaurs fit in isn’t clear yet.

What is apparent from the fossils is that they had feathers on their feet, the four wings on the title. Xu Xing, the Chinese paleontologist studying the fossils, remarks that no contemporary birds have feathered feet, which indicates his unfamiliarity with chickens. Many breeds have feathered feet – bantams are divided into Clean-Legged and Feather-Legged classes. So the fact of feathered feet is not in itself remarkable.

The fossil feathers are different, the flight feathers of wings, rather than the fluffy feathers of Brahmas and Booted Bantams. This photo of a Sultan chicken, an exhibition breed developed in Turkey, from My Pet Chicken,, shows thick feathering on the feet. It's easy to imagine that it wouldn't take many generations to breed for asymmetric flight feathers.

As the illustration shows, this critter had four wings. The show goes on to explore how it might have flown, including wind tunnel tests conducted by engineers from Brown University's Flight Mechanics Laboratory.

It’s an interesting show all around, bringing insight into how birds came to be, and came to fly.

Artist Jason Brougham of the American Museum of Natural History shows how Sinornithosaurus ("Chinese bird-lizard") might have looked with a full set of feathers.

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