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Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)




----- Original Message ----- From: "Michael Habib" <mhabib5@jhmi.edu>
To: <dinosaur@usc.edu>
Sent: Friday, September 26, 2008 9:32 AM
Subject: Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)



I'm not sure I'd frame a separation between gravity and muscle power usage, however. Even in those groups where arboreal stages have been critical to the origin of flight, it is quite likely that powered leaps were involved - there is no reason to assume that flight evolution needs to be begin with simple falls (especially for a group such as birds, which inherited a strong leaping apparatus). This is yet another reason why setting a threshold between arboreal and terrestrial origins is difficult and misleading - both may actually involve very similar launch dynamics.

This is very similar to my own thinking.

Granted, but if the evolution of powered flight in a given group involves movement between the ground and trees, or involves an intense mosaic of both arboreal and terrestrial forms, then we will probably never have the resolution required to pin down the ecology of the "first" ancestor in the sequence. And besides, if that "first step" happens to be populations that use both trees and ground running, then the dichotomy is really broken.

And that as well. JimC