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Re: Perching, climbing, roosting was Re: 11th specimen of Archaeopteryx



Anthony Docimo <keenir@hotmail.com> wrote:


>  So dinosaurs require special pleading?


Now that you mention it, yes.  Yes they do require special pleading.
Simply invoking snakes and frogs and possums, and how easy these
critters can switch between a terrestrial and lifestyle, and then
saying dinosaurs could do it too... it just doesn't mesh with the
anatomy of non-avian theropods.



>  We *know* a transition occurred - we have birds these days, after all.  It 
> *is* possible.  *Nobody* said it was easy.
>
> But some people are saying its impossible.


I'm saying where's the evidence that non-avian theropods could perch
or roost in trees?  No matter how intuitively attractive the idea is,
it needs supporting evidence.


>  and I was pointing out the broad diversity of branch location - not that 
> protobirds always used all branches


Where's the evidence that basal paravians used ANY branches?  The
anatomical evidence indicates that confuciusornithids, sapeornithids,
many enantiornitheans, and some basal euornitheans could perch on
branches.  But no theropod outside the clade formed by these taxa
shows any evidence of perching.  Although I'm intrigued by the
(unpublished) study suggesting that _Jeholornis_ had an incipiently
retroverted hallux.


>  seriously, it doesn't matter what the backbone or shoulder looks like.  no 
> part of mammal anatomy lets you ignore the laws of physics
> and plant biology (namely that the crown is always above any trunk, so you 
> always have to cross the trunk if you're crawling from the
> ground to the crown - it doesn't matter what part of Kingdom Animalia you are)


Therian skeletons are ancestrally adapted for both scansoriality and
arboreality.  They could climb trunks as well as they negotiaed
branches.


"Kingdom Animalia"??!!  Where are you writing from - the 1980's?






Cheers

Tim