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Re: Climbing Mononykus

Richard L. Dieterle wrote:
> (etc.).  I would suggest that the following are serious problems for this 
> view:
>(1) the muscle attachments indicate that the power of the arms was directed
> inward; 
(2) the claws were also pointed inward; 
(3) ex hypothesi, the front legs
> have undergone radical adaptive changes to rock-climbing while the back legs 
> and
> feet remain, even by Theropod standards, relatively primitive and not 
> obviously
> specialized for rock-climbing; and 
(4) if we are to imagine Mononykus as
> quadrupedal, how could we then explain the peculiar foreshortening of the 
> front
> legs?  Also, is it not true that mountain goats primarily locomote in rocky
> terrain by leaping?  I sure would hate to land on two stubs terminating in
> giant, pigeon-toed claws.  However, even in the bipedal, upright climbing 
> model,
> the arms are so small in relation to the legs, one wonders how the two sets of
> limbs would coordinate in this enterprise.  The same holds for climbing trees.

I was picturing it more as a setter on it's back legs (setting like a
duck amongst a pile of rocks) and walking the upperarms around while
leaning forwards while looking for lizards or grubs or whatever, thus
the back legs would be folded and immobile so that the lengths are not
so different, but your other two points are well-taken and show that
this 'tip-walking' of the front arms is unlikely.  This might be
effective in the type of terrain in modern day California-mountains with
deposited or eroded rocks with lots of uneven pockets of soil trapped
around them-not so much the Mountain goats' sheer cliffs.  I picture it
more like that of the Bighorn sheep's terrain-more valleys so not quite
as strenous a climb.  (Wouldn't Paul Bunyon be proud!)
Perhaps this inwards-pressure allowed for both hands pressure-gripping
items for carry (such as eggs or carcasses) but the power needed for
that seems a little over-kill compared to the grappling ability of
longer-fingered animals like Deinonychus (much more capable of delicate
gripping), and the claws would seem to need to be sharper-they still
seem pretty blunt.
           Betty Cunningham  
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