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Re: Climbing dromaeosaurs?

Stanley Friesen wrote:

<Quite - and many climbers use hands and feet to climb.>


<I do not think this is really relevant, as it is about *perching*,
which is quite different mechanically than climbing. Most birds,
except those that feed on tree trunks, do NOT climb, they don't need
to, they can just fly to the branch. One really wants to compare claw
structure to real climbers.>

  Forgetting about woodpeckers walking up trees....
  Based on a wolf-sized animal, there are several extant animals that
climb regularly: young cougars and leopards and jaguars, some monkeys,
young gorillas [this is not supposed to be a complete list].

  All climb up trunks by splaying their forearms around the trunk
either sideways or above their heads, and the hindlegs are below and
under the body, more medial (closer to the midline) than not. For
those with limited access to such wonderous sights, cats and squirrels
climb the same way---mostly. Arboreal monkeys and everything else
listed except gorillas have strongly curved claws with either a flat,
round, or grooved ventral edge.

  Dromaeosaurs have rounded surfaces to their claws, as Tom Holtz and
others have pointed out before. The only abberant is *Utahraptor* with
its laterally flattened blade.

  Gorillas grasp the trunk much as we do (when we're not wearing
cleats and using climbing ropes or such gear) and mostly use the
strength of their legs to push up.

  Jessica's scenario of a climb is basically correct. However,
squirrels and cats will spiral as well as go strait, but I know of no
larger animals that "spiral", and this may be mass related or not. The
dynamics of "spiralling" generally entail pushing yourself (against
gravity and your own bulk) sideways, pushing up with one foot---the
other foot is in the air, suspended before it contacts the tree at the
end of the "spiralling" "jump".

  One would think *Utahraptor* wouldn't be able to climb, with its
blade like claw and larger bulk than anything except a gorilla or
maybe a really large jaguar. But I think it is possible, perhaps
temporarily, one group of Nyasa (?) lions are habitually obligate
arboreal, and their mass may parallel that of *Utahraptor*. Narrowness
of claw may not be as important as the muscular strength of the foot
and/or the second pedal digit. I would like to see a study of this, if
there hasn't been one published. *Veloviraptor* has the most complete
dromaeosaur skeletons, and hindlimbs, so that may be a logical place
to start.

Jaime A. Headden

Qilong, the website, at:
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