Hot off the presses from the Proceedings of the National Academy of Sciences, we have a paper in which a theropod dinosur, Microraptor gui (a feathered dino closely related to the ancestor of modern birds) was found with a bird in its stomach. M. gui is famous for being a “four-winged” dino that had all four limbs feathered but probably didn’t fly.
I’ll present the results without comment, except for a brief note at the end.
The fossil and schematic diagram (click to enlarge):
What does it mean? M. gui probably couldn’t fly (but might have glided), yet it clearly spent time in the trees preying at least partly on flying birds. This lends some support to the “arboreal” (top-down) scenario for the origin of flight, whereby flight originated from tree-dwelling theropod dinosaurs as a modification of wings used for gliding and controlling descent. The other hypothesis, the “cursorial” (bottom-up) hypothesis, whereby flight evolved from feathered dinos running on the ground and flapping their proto-wings, perhaps to aid running, jumping and gathering food, isn’t really supported by this paper, but it isn’t ruled out, either.
For more, see the paper here.