This is actually an older drawing that I came across while rummaging through a sketch pad buried in some unexplored region of my desk. It's part of the series of dragons I was posting earlier (Torgadon and two-headed dragon), and will be added to that collection in the Doodles and Art tab up above.
The creature itself looks as if it was evolved for flying long-distances, with its large, gliding wings and light build. The little leaf-shaped fan on the tail would serve as a rudder when flying, and the wiry muscles around the shoulders and wing bases would be designed for holding the wings in a gliding position for long periods of time without tiring.
I'm not entirely sure what my idea was with the rider on its back. I designed her armor after the dragon's chin frills, and I gave her a long broadsword since that would be the easiest weapon to use when lying on your stomach fighting atop a large animal.
I haven't yet come up with a name for this creature, but a friend of mine thought it should speak in a Brazilian accent.