When Archaeopteryx was first discovered, it was the earliest known feathered dinosaur, and the argument that it was evolving towards flightlessness might have been considered madness. (scientificamerican.com)
Big ground birds like emus and moas may look alike, but they are only distantly related, and flightlessness evolved six times within 10 million years (newscientist.com)
According to the researchers, their findings indicate giant sizes appeared early in penguins» evolution, «soon after flightlessness released penguins from aerodynamic constraints.» (science.howstuffworks.com)