I haven't really given much thought to what forest flyers actually look like. Considering they're likely the most common house pet among yinrih I think I ought to change that.
I describe them as having many of the same cultural associations as cats, so subconsciously I've pictured them as cats, perhaps with a potagium for gliding.
Another possibility that occurred to me today is that there may be two separate clades of terrestrial vertebrates, one with four limbs and one with six. These hexapods could potentially evolve wings from the middle pair of legs. Perhaps the hexapods and tetrapods emerged from the oceans at different times, or perhaps the tetrapods evolved from the hexapods.
Perhaps wormcows are part of this hexapod clade.