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Re: Phytodinosauria status



In a message dated 6/7/01 1:59:01 PM EST, david.marjanovic@gmx.at writes:

<< Here you IMHO run into the same problems as Feduccia -- why should the
 forelimbs (and only they) evolve into wings in a quadruped, and why should
 they lose digits in an arboreal animal??? >>

They can easily evolve into wings in a leaping quadrupedal arboreal animal, 
since they are no longer entirely involved in physically supporting the 
animal but have become involved in aerodynamic control (along with the tail) 
during the leap phase and in helping the animal to alight at the end of a 
leap (furcula is the shock absorber for this). Digits were lost from the 
outside in because these digits in particular ruined the aerodynamics of the 
feathered wing. The feathers were there long before the wing, of course, and 
the wing itself goes back to before Herrerasaurus, which already shows strong 
reduction of manual digit V. Evolution of the wing is the reason manual 
digits IV and V are reduced/lost in all post-sauropod dinosaurs.

The hind limbs were still needed when the animals were grounded; a running 
start, for example, might have been the way they took off from the ground 
when the wings were still unable to provide all the energy for that job 
themselves.

The problem I have with the usual scenario is there is simply no way the 
small, grasping forelimbs of a Coelophysis-size theropod could have evolved 
into wings. What possible aerial function would such pre-wings of a running 
theropod have? (Or are you one of those who imagines that the wings of birds 
evolved all their aerial features on the ground, and then as if by magic the 
animals were suddenly able to fly, never having previously touched the air 
with wings?) Feathered pre-wings would get in the way of any predatory 
grasping function but provide no compensating payoff. And just because >I< 
may be too stupid to think of such a payoff is not an argument >for< such a 
payoff, either. Nobody else can come up with one, either.