Sorloc

I know that common thought has them as reptilian, perhaps Varanidae or Agamidae (Monitors or Flying Lizards), but would it be possible for them to maybe be more closely related to the bat? It seems a shame that we don't have any six-limbed vertebrates; there are so many mythical creatures that seem scientifically impossible - Centaurs, Hippogriffs, Gryphons, and of course, Dragons.