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

[jrc <jrccea@bellsouth.net>]

----- 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