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

[Tim Williams <twilliams_alpha@hotmail.com>]

Augusto Haro wrote:


> More in the sight of the baboon case (the other seem untestable), I think
> that if you have a cursorial clade, from which some individuals become
> arboreal, it may occur that some of the basal members of the arboreal clade
> present a majority of cursorial adaptations accompanied by few arboreal
> ones. 


I see what you're saying here, and I agree.  If behavior precedes novel 
adaptations, there is a 'lag' between when theropods first became arboreal and 
when they first show arboreal adaptations (like perching).  I don't doubt that 
this is exactly what happened.  _Archaeopteryx_ and microraptorines might 
represent incipient stages of arboreality.  Thus, both retain their 
plesiomorphic cursorial adaptations, while acquiring novel scansorial 
adaptations.


However... my argument against a specialized gliding stage (e.g., 
"tetrapteryx") in the origin of avian flight is that this implies that 
specialized arboreality preceded _Archaeopteryx_.  If (say) birds evolved from 
gliding quadrupeds that first appeared in the Triassic (as 
Martin/Feduccia/Czerkas/etc allege), why does Late Jurassic _Archaeopteryx show 
so few (if any) arboreal adaptations?  In other words, if _Archaeopteryx_ 
supposedly represents the culmination of 70 million years of life in the trees, 
why does it lack even the most basic arboreal adaptations (and have so many 
cursorial ones)?  BTW, I'm not saying this what you're claiming, Augusto.  I'm 
just seeking to emphasis just how "forced" these claims about _Archaeopteryx_ 
being a specialized arboreal animal are.


> But now I am thinking that the trees-down theory does not need from
> obligatory arboreality. 


Yep!  Now you're talking!  :-)


Cheers

Tim

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