I am working on an alien species with mammal-like features and characterized by radial symmetry, in opposition to bilateral. They have four lower limbs arranged in a square-like disposition, with the palms all facing outwards(they have ape-like hands), sustaining a central torso which grows out of the junction; the animal is meant to have a pretty heavy build.
In order for it to really be able to functionally operate with a 360 degrees angle, I need the head and arms to be able to move independently of the central torso, given that full torso rotational capacity is out of the question, and it's not even that pretty.
The head problem is solved by owl-like adaptation, only amped up. But I am not sure how to go about the upper limbs matter.
I have thought of simply giving them four arms, and possibly of extending that to having two sets of forward facing eyes on the "front" and "back" of the head, which would allow the functionality provided by radial symmetry to be maintained with a "static" configuration, rather than one requiring active movement on the part of the animal.
Yet, that is not really the concept I had started with, and I would like the animal to only have 6 limbs overall, since with eight I feel it's already losing too much of the mammalian "feel"; in the end it will come down to how much I want to adhere to "science", but I want to listen to this "side of the equation" and consequently I am very interested about your opinions : would it be possible for the upper limb junctions of this animal to roate in such a way that full functionality is always maintained?
The only thing I can think of is that it may perhaps be able to fully rotate its arm at the shoulder junction, and given that the alien has its five fingers pentagonally arranged around its palm, the problem of the human thumbs changing place is not there.
I am not asking about the likelihood of such a being evolving given our current knowledge of the evolution of life on one single planet, yet that's where we must start, of course. It is clear, however, that out-of-the-box thinking has to be used in these matters.
And besides, would an arachnid-like leg structure (and consequent gait) be feasible for such an animal (7-15 tons range)?
Edit : I would also add, I mean the upper limbs to be articulated. I have thought of the possiblity of them having proboscis-like limbs, which would indeed solve the problem of rotation given that there would be no junction, but the fact of the matter is that, again, it doesn't fit with the "feel" I want the alien to stimulate. Besides, in the same story there are already creatures which use such a tentacular configuration, and I'd rather avoid redundancy.