TWO WINGS GOOD, FOUR WINGS BAD:

Four-Winged Dinosaurs and the Dawn of Flight (Kate Wong, January 23, 2003, Scientific American)

The ancestors of birds may have taken to the air on four wings and a prayer. Paleontologists have recovered from deposits in Liaoning, China, dinosaur fossils that exhibit evidence of flight feathers on their hindlimbs as well as their forelimbs. The specimens are said to represent a long-sought intermediate stage in the evolution of birds from flightless theropod dinosaurs, and could breathe new life into the theory that protobirds glided between trees before developing powered, flapping flight.
Evolutionary biologists have long debated whether birds began winging it by gliding among the trees or by racing along on the ground. The latter scenario has gained favor in recent years. But the new finds, described in a report published today in the journal Nature, "provide negative evidence for the ground-up hypothesis" and instead support the arboreal gliding scenario, assert study author Xing Xu of the Chinese Academy of Sciences and his colleagues. [...]

Xu and his collaborators base their conclusions on the long aerodynamic feathers that cover the fore- and hindlimbs of Microraptor according to the same pattern seen on modern bird wings. Long feathers around the ankles would have made traveling on the ground difficult. But the forelimb and hindlimb feathers "would make a perfect aerofoil together," the authors write, likening it to the membrane employed by bats and gliding animals.

Well, obviously not perfect, or natural selection wouldn't have disposed of them, would it? Posted by Orrin Judd at January 25, 2003 4:42 PM