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Re: Fwd: Aw: RE: Arboreal Theropods: The prize at the bottom of the cracker jack box



Tim Williams wrote:

>Don Ohmes wrote:
>
>> Analog, schmanalog. The mechanics of standing on a horizontal rigid branch 
>> are the same as standing on
>> flat ground -- whatever your neutral pose is
>>
>> It is irrelevant, ecologically...
>
>It is?  You're a biped (I assume). Give it a try.  Is standing on a
>branch really as easy as standing on flat ground?  :-)

A horizontal branch that 2x the length of my foot in diameter presents little 
challenge, in my experience.  And a branch 2x the diameter of the impressively 
clawed M zhaoianus foot is quite a small branch...

>Birds that roost in trees *typically* have a grasping pes, even if it
>is not optimized for perching; the hallux is reversed, and able to
>oppose the other three toes in anisodactyl grasping.  I know not all
>roosting birds do this.  But to argue that this feature was not
>required for roosting in non-bird maniraptorans strikes me as special
>pleading. 

The above is special pleading of the most brazen sort. It boils down to a 
decree.

The turkey is presumably descended from an ancestor with the iconic "perching 
pes", and roosts nightly -- yet the hallux has *become* vestigial relative to 
grasping function -- as one would expect, given it's foraging habits. 

Reality and evolutionary logic stand contra the contention that sheltering in 
trees inevitably alters the foot -- and rebuts the contention that a trees-down 
path to flight is necessarily associated with "arboreal adaptations".