Whatever the tag for "normal" zoomorphic bodytype ("feral") ends up being, it shouldn't NOT be "quadruped". Non-anthro birds and kangaroos are bipeds, as are some dinosaurs and dragons. A variety of fantasy creatures have a leg number that is not four. Centaurs aren't "feral" but they _*are_* quadrupeds.
It would also stir up a real mess with the pre-existing mess that is "[bipedal":](/tags/bipedal), which currently is not a bodyplan tag but a pose tag for zoomorphic quadrupeds.