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Re: Climbiing Dinosaurs (RE: a little background) T.F.



> Mike S. wrote
>
> I agree with Tim Williams.  It is a nice naturalistic rendering of a
> climbing dromaeosaur!
> Just to confirm, are you saying that the position and orientation of the
> forelimb in the illustration represents the farthest forward (cranial)
> excursion the humerus can make without being separated from its' contact
> with the glenoid?
>
> I've been discussing the idea of tree climbing in dromaeosaurs with Bob
> Bakker recently ( we're working on a book together).<<
> Really? Cool (I just hope you have a good contract) and it's about time
Uncle Bob came out with a new book!

We ( Bob and I) are both working together with Random House on this
(although contracted separately) for one of their "Step into Reading" books
( similar to the "dinosaur - bird connection" book I did with them last
year ).  Random House has been a very good publisher to work with and are
definitly progressive in their approach to developing childrens dinosaur
related books. They've been using paleoartists for the visuals (most
recently Bob Walters and myself) and I believe I've convinced them that
having paleontologists write the text for upcoming titles is also to
everyones advantage,  getting the best information right from the source.

> >>One of the arguments some individuals at last SVP were making against
tree
> climbing was, of course, that if the animal attempts to retract the
humerus
> (in pulling its body upward), that the mechanics of the forelimb want to
> force the arm to "collapse" as it is designed to do, which would then
negate
> its ability to move upward.  As you rightly point out, what may be more
> important here is that the arms in extension remain in a relatively static
> position, simply supporting the body weight AFTER the legs have thrust the
> body upward ( and while the legs are then drawn up under the body for the
> next thrust upward ). So really then, all the work in tree climbing
> dromaeosaurs is done through leg propulsion with the arms and tail
> secondarily helping in manoeverability, in more lateral movements onto
tree
> limbs, etc...  The only thing that appears to me to be slightly
problematic
> is moving its body and tail through more densely limbed conifers, if they
> attempted that.  I strongly suspect however, that even that was possible,
as
> I'm sure dinosaurs were as capable in their own environments as most
modern
> vertebrates are in theirs today.<<
>
> If we take into account Kenneth P. Dial's theory (On the origin and
ontogeny
> of avian flight: wing-assisted incline running) Dromaeosaurs didn't have
to
> use their arms to climb. Just 'flap and run' up the tree till it got to a
> branch, then it could use its arms/hands to climb. This was the best talk
at
> the SVP for me.

Good point.  Smaller dromaeosaurs may have been able to move vertically up
larger (obliquely oriented ) tree trunks before even having to employ manus
claws as anchors.  Ken's talk was one I definitely regret NOT seeing.  I
hope he either modifies it, or presents a sequel to it, at this year's
meeting.

Since the focus of the book I'm illustrating for Bob will be on Deinonychus,
I think the strategy for scaling tree trunks may have to be modified beyond
the "running up" technique to more of a "leap and grab" system.


> Mike Skrepnick