Re: Thou Shalt Not Climb!

[mariusromanus@aol.com]

(In reply to David's post)

Ummm... I think my point is being thoroughly missed....

In the nutshell, this is what I am asking;

Were basal birds up in the trees before they had the modern traits we 
now use to define a bird as arboreal???

If not, then why did selection select for an arboreal lifestyle?

Whales, before getting wet, didn't just lose their hind limbs, sprout 
flukes, and head for the sea, right?


Kris
Saurierlagen@gmail.com





-----Original Message-----
From: David Marjanovic <david.marjanovic@gmx.at>
To: DML <dinosaur@usc.edu>
Sent: Mon, 25 Jun 2007 5:18 am
Subject: Re: Thou Shalt Not Climb!


> Could someone be so kind as to explain to me why is it, that aÂ
> theropod is automatically banned from the trees unless its firstÂ
> toe is reversed???Â
Â
It isn't. It's just that in the absence of such adaptations we have no 
evidence that it ever _was_ in the trees.Â
Â
> On that note, what about the curved phalanges in the manus ofÂ
> Archaeopteryx? Why can't these be interpreted as an indication ofÂ
> climbing?Â
Â
They clearly made climbing easier than their absence would.Â
Â
But they clearly didn't evolve _for_ climbing. They are ordinary 
theropod finger claws, a _retention_, not an adaptation that evolved in 
*Archaeopteryx*. Archie simply lacked selective pressure that would 
have led to the _loss_ of the curvature.Â
Â
> After all, monkeys and squirrels have the same trait.Â
Â
So do *Gigantoraptor* and *Allosaurus*.Â
Â
> Also, the orientation of the unguals on the manus, as well as an 
increased > range of motion for the shoulder joint in basal birds and 
their kin, look > to me like something that would come in handy when 
climbing...Â
Â
Sure. But the increased range of motion is still pathetic by comparison 
to extant climbing animals.Â
Â
> And what about the pecs?Â
Â
The what? Pectoral muscles?Â
Â
> Why would such a scenario not be possible?Â
Â
It is possible. But that's not what we're asking. We ask "is it 
testable" and "how can we test it". Â


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