Re: climbing dromaeosaurs and friends

["Scott Hartman" <scott_hartman@hotmail.com>]

Everybody,
    The problem isn't simply whether or not maniraptorans could climb trees 
(and in this regard, I think Gishlick's analysis is pretty good) but whether 
they were arboreal _scannsors_.  And they couldn't have been.  As I 
mentioned (briefly) in my talk at SVP, the parasagital limbs of theropods 
put their center of mass too far away from the substrate (branches) to have 
been succesful scannsors.  If they had tried to jump from branch to branch, 
they would have fallen on the very first try.  This appears to have been 
true even of Archaeopteryx, and it is unlikely that early birds were 
arboreal themselves until they evolved a degree of control that allowed for 
low speed landings.
    Of course it's fair to question whether perhaps some theropod limbs 
didn't operate in a parasagital plane; Larry Martin has suggested that 
Arcaheopteryx limbs were "monkey-like" in their articulation.  The utter 
lack of acceptance of this idea is evidence itseld, but taphanomically it's 
also pretty unambiguous.  All of the Archeo specimens, despite their myriad 
preservational positions, preserve the hind limbs in a parasagital plane 
(even when the forelimbs aren't).  Yet the far majority of articulated 
Solenhofen pterosaurs are preserved with the hind limbs in separate planes 
of articulation.  Clearly something functional is different between these 
taxa.
    So what of all the papers (e.g. Feduccia) that suggest that Archeo was 
a percher, and now perhaps Microraptor was also a good climber?  It's a load 
of dingos kidneys, I'm afraid.  All of the pretty diagrams comparing Archeo 
claws to perching birds, running birds, etc. always fail to include 
falconiformes, which use their claws for prey manipulation.  When these 
critter are included, as in the study presented by Kenworthy, Chapman, 
Holtze, and Sadlier, Archeo groups much better with prey-manipulation claws 
than it does with perching claws.  In fact, I would go so far as to suggest 
that the retroverted hallux evolved for prey manipulation long before it was 
useful for perching, although this evolutionary novelty certainly 
pre-adapted birds for a perching lifestyle.

Well, that's long enough for now, I'll rant on birds and arboreality again 
later.

Cheers,

Scott
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