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Re: Fw: Dinosaurs and birds




----- Original Message ----- From: "don ohmes" <d_ohmes@yahoo.com>
To: <dinosaur@usc.edu>
Sent: Tuesday, April 10, 2007 1:32 PM
Subject: Re: Fw: Dinosaurs and birds



Quick re-cap of the debate (started w/ a resolved miscommunication) as I understand it (corrections welcome); I say ground-up flight evolution scenarios that pre-suppose flat terrain and advantage conveyed by increases in maximum speed generated by "wing-assisted" (=forelimb assisted) aerodynamic thrust are feasible, and even likely,

I'd say that ground-up scenarios that don't presuppose an increase in maximum running speed due to flapping are also feasible and even likely. Transient gusts play a huge role in assisting ground up flight scenarios, and they don't even need to be substantial gusts. Lift increases with the square of the gust speed, so even a 40% gust speed will temporarily double available lift, and the animal can then use gravity to accelerate and maintain that lift while returning to the ground. Running speed isn't terribly important to the ground-up flight scenario. I believe that this is pretty much what Mike thinks as well, but I don't want to put words in his mouth.
JimC