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Re: Various thoughts re: implictions of _Microraptor_ and bird flight origins
In a message dated 1/24/03 5:27:12 AM Pacific Standard Time,
<< B) In my view, Dial's discovery demolishes the split between "ground up"
"trees down": it shows that people have been talking at cross-purposes.
Despite what people have been arguing for years, this isn't an "either/or"
situation, but might better be explained as two different steps in bird
flight origins, with Dial's Wing-Assisted Incline Running (WAIR) as the
functional missing link between the two. >>
Actually, it demolishes the "strict ground-up" theory, in which flight is
purported to evolve in ground-dwelling dinosaurs with >no< arboreal component
in their lifestyle, through an accumulation of flight-related characteristics
each of which appeared for a non-flight reason (such as predation) and was
exapted for flight by the organism once it acquired enough of them to fly.
This was the prevailing theory among "birds are dinosaur descendant" workers
until the small, feathered, and obviously arboreal theropods were found at
Liaoning. Thereafter they started to back-pedal. Just search the archives of
dino list for the mid-to-late 1990s and you'll find enough posts to
WAIR behavior would have been available to Permian prolacertiforms, among
which are a number of winged gliding forms as well as the ancestors of the
pterosaurs (a la Peters) and the archosaurs (a la me and many other workers).
We haven't found exactly the right ancestral prolacertiforms yet, but they
could turn up at any time.