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Re: Perching, climbing, roosting was Re: 11th specimen of Archaeopteryx

2011/11/12 Anthony Docimo <keenir@hotmail.com>:

>  Really?  What part of a goat is adapted for gripping branches?
>> So knowing this, you wouldn't have to be a crazy person to look at a
>> goat fossil and say, "Yep, foraged in trees".
> http://2.bp.blogspot.com/_GhcCFcMfw-k/TSn5c-4PetI/AAAAAAAAARA/1noTX2bLcMk/s1600/goatskeleton.gif
> I don't think we could look at it and say "definately a mammal, so therefore 
> it could climb trees with ease."

I would rather say that ungulates are, among mammals, the most
analogous in locomotive incapability in trees. Ungulates (artiodactyls
and perissodactyls at least) have reduced adductors and abductors,
rotators of the limb segments, and reduced the number of toes which
may grasp branches. Their limb movements are almosty completely
restricted to the parasagittal plane, as seems to be the case with the
hindlimb of dinosaurs. They even lost the recurved claws when getting
hoofs. Their trunk vertebral column is similarly stiff.

So, it seems easy to see why few ungulates can climb trees. Even the
goat species which climb trees do not seem to be all the time
climbing, that's why they are surprising. I would rather think it is
the capability to stand upon a very little substrate surface which
enables goats to climb trees with relatively low canopies (to which
they can reach just jumping). In this they may surpass most dinosaurs,
as there are no dinosaurs which is as much unguligrade (which I know!)
or poses on so few digit tips. But as far as I know, goats do not have
specifically tree-climbing traits.

Besides this capability on the side of the goat, I have no much
problem in seeing small dinosaurs, either ornithischians or
saurischians climbing similarly low trees (even similarly
incapacitated dogs, whose limbs mostly move parasagittally, can climb
low trees). However, as Tim says, we have no positive evidence
suggesting they were specialized to live there, and as they have
mostly cursorial adaptations, it is more likely they were most of the
time in the ground.