Many possible causes. Many things can cause calluses. Some reasons that one may develop a callus include: viral infections (warts), friction, pressure, repedetive trauma, and a limitation of joint motion. Some genetic conditions may also cause people to develop calluses on the hands and the feet. Treatment depends on the cause of the problem. Have it evaluated by a professional and get the appropriate treatment.
Dry feet. Yes. It can be very bad to have dry feet. Your feet can dry out to the point where they crack open (like the dry desert earth). When this happens there can be open sores. Open sores on your feet are never good due to the fact that there is a high potential for infection. Do the easy thing and use hydrating lotion daily especially after getting feet wet. Cocoa butter daily can do wonders.