Some dune types on earth, such as transverse and longitudinal, can take long, winding forms. In the case of transverse dunes, the ridge is perpendicular to the direction of the wind, in longitudinal, the ridge trends in the direction of the winds. In my opinion, these are natural features not unexpected from what we currently know of Martian geological processes. The second dune is most of the time smaller than the first, and the difference of width is usually proportional on both sides. This is due to the physical characteristics of the wind on forming such things.
Dunes run parallel due to the wave properties of the air.
Besides you may note that there seems to exist even a smaller third dune in that place. Following the successful Pathfinder landing and rover deployment on an ancient flood plain on Mars, anomaly researchers wondered if NASA would seek out some vaguely face-like features on one of the rocks scattered about, and use this to ridicule those who take a serious interest in the Cydonia Face. One correspondent who called me had the impression that it was the Egyptian structure that was on Mars. Unfortunately, the faces and inscriptions some have seen on the rocks are not three-dimensional objects as is the Cydonia Face, do not possess the elements of detail noticed at Cydonia, and are not located in a context that provides significant support for the speculation that they are deliberate carvings. These are not visible in NASA-released photos.