CLIMBING

["Matthew Troutman" <m_troutman@hotmail.com>]

<<I do not disagree with George, Feduccia, Troutman, or you, Wagner; nor 
all the others who either oppose or support BCF, BADD, BAMM, or BAND. My 
point here is that each theory is strong in one suit, and this recent 
proposal has merit into the possibility above. None of us is wrong. None 
of us are sure (or can be sure) we are right, just that we can get damn 
close!>>

This is close to what I support.  I say that climbing had a big part in 
avian evolution, but not to the extent that you support in dinosaurian 
evolution (maybe I'll support it later).  I can believe that it was 
important for maniraptoriforms (all coelurosaurs?), but not the whole 
for theropodian evolution.  I could elaborate further but I'll take the 
5th for now (don't worry, soon you will know my thoughts on climbing).  

But let me go onto:

THINGS THAT MAY NOT RELATE TO CLIMBING

One big thing on my list is vertebral pnematization.  Yes, it CAN 
lighten weight (most vocal advocate: Paul Buhler; see Buhler 1992) by 
means of reducing bone in the body of a bird (for more thoughts on 
pnematization read Witmer 1997).  However, we cannot be sure how this 
may relate to theropods because you can consider it evidence for 1) a 
more avian lung system; 2) evidence that theropods had extensive lung 
septae, but not air sacs.  Neither of these directly evolved for 
lightening weight, both are just extensions of the respiratory system 
with 1 being the most active, dynamic system in use.  I stand by 
Witmer's (1997) conclusion that pnematization by use of air sacs is 
something that can be exapted for many things.  Yes, they may have been 
exapted to make a lighter weight, but this in itself does not directly 
support the climbing hypothesis because the easiest way to reduce weight 
is to evolve a small size.  

Recurved claws (of certain form) do not relate to climbing because some 
non-climbing birds have strongly recurved claws (eg. falconiforms, 
strigiforms, perching birds).  To be for absolute sure whether a claw 
was used for climbing or not you have to look at it from several views 
(also review discussions in Yalden 1985; Peters and Gorgner 1992; and 
Feduccia 1993): lateral (taking angle measurements); and dorsal 
(checking for a conical, rounded shape like in predatory birds and also 
checking for extreme lateral compression).  One thing that should be 
noted is that in cliff dwelling birds the claws are virtually identical 
to trunk climbers but display little distal wear (see Peters and Gorgner 
1992).  No discussion about claws would be complete without discussing 
_Archaeopteryx_  and its famous carpal claws.  Peters and Gorgner (1992) 
and Padian and Chiappe (1998) both considered the lack of distal wear in 
_Archaeopteryx_ claws as evidence against the trunk-climbing hypothesis.  
However, they both decided not to look at trunk-climbing mammals (which 
are a better analog to _Archaeopteryx_ because they both would use both 
limbs during climbing) and the trunk-climbing animals which I have seen 
lack extensive, picine-like distal wear on their manual claws (see 
figures of _Cynocephalus_, _Hipposideros_ and _Pteropus_ in Yalden 
1985).  So you have to look at the form of the claws to be for sure 
whether or not they are climbing form (contary to viewpoints expressed 
variously by Padian and Chiappe 1998, the claws of _Allosaurus_ and 
_Tyrannosaurus_ do not equate well with climbers).  

Bipedalism does not equate with climbing either.  True, some climbers 
are bipedal climbers strictly such as picines (see Bock and Miller 
1959), but most non-avian climbers climb quadrapedally.  This does not 
argue against climbing in theropods for the tree kangaroo, 
_Dendrolagus_, is a bipedal animal that climbs and the (juvenile) 
hoatzin, _Opisthocomus_, is faculatively (to a point) bipedal but climbs 
(and scampers along the ground and swims) quadrapedally.  Primates all 
climb quadrapedally.  

Remember these exceptions,

Matt Troutman

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