Tuesday, October 11, 2011

Origin of flightlessness

This research requires some changes be made to what I have proposed concerning flightless birds. Flightless birds will have to be integrated into multiple lines. For simplicity I had them in one single line.


"Their molecular dating study suggests that the ancestors of the African ostrich, Australasian emu plus cassowary, South American rheas and New Zealand moa became flightless independently, in close association with the extinction of the dinosaurs about 65 million years ago.

"Many of the world's largest flightless birds, known as ratites, were thought to have shared a common flightless ancestor. We followed up on recent uncertainty surrounding this assumption," said Dr Phillips.

"Our study suggests that the flighted ancestors of ratites appear to have been ground-feeding birds that ran well. So the extinction of the dinosaurs likely lifted predation pressures that had previously selected for flight and its necessary constraint, small size. Lifting of this pressure and more abundant foraging opportunities would then have selected for larger size and consequent loss of flight.

The finding of independent origins of flightlessness also solves a mystery of how these flightless birds dispersed across the world over marine barriers -- their ancestors flew."

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