You're right about flies and maggots in extremely arid conditions. The conditions are too hostile for them to survive. Normal putrefaction cannot happen.
In most deserts, there is some degree of wind movement throughout the year. A dead body will more often than not become covered with a substantial layer of sand within a few days. The hot sand absorbs fluid from the body, starting with the skin. Over a period of weeks or sometimes months, this absorption can result in complete dessication of the body and the body will become mummified.
The resulting cadavers are obviously far lighter in weight than normal cadavers due to virtually complete absorption of water. The skin on such cadavers is extremely tight and will often have split around the areas of maximum tension such as the axillae (armpits) and groin. Due to the tight skin, the outline of the bones can be seen through the skin.
if left undisturbed, such cadavers will eventually crumble away.