So fantasy dragons and Avatar notwithstanding, six limbs on a land dweller is pretty weird. I'm going to have to question this creature either being real or actually having four-wings and a pair of legs.
edit Looking a bit more into it, it looks like the artist's picture is a hopeful fantasy. The class of animals were more like flying squirrels in the sense that they used their hind legs for lift as well. So they're four limbed animals.
Dinosaurs are part of the tetrapod clade, so I never expected "four-winged" to mean anything other than that the hind limbs and forelimbs are both feathered and used for flight. That's what the artist's conception based on the discovered fossils shows.
Oh wow. I think I need more coffee. The first few times I looked at the artist's rendering, I swear I thought it was a 4 winged, two legged animal. But you're right, they rendered it as a tetrapod.
The drawing is very confusing. It looks as if the back wings are just obscuring clawed legs rather than being the legs themselves. I had exactly the same thought as you and came here to comment the same thing.
http://www.thegeektwins.com/2010/06/flawed-science-of-avatar...
edit Looking a bit more into it, it looks like the artist's picture is a hopeful fantasy. The class of animals were more like flying squirrels in the sense that they used their hind legs for lift as well. So they're four limbed animals.
https://en.wikipedia.org/wiki/Microraptor