For my part, don't think of them as your Smaug, that's the dream dragon all sleek with scales and bat wings, but think of them as pieces of the landscape that form into a dragon shape, but crudely and clearly still made from rocks and boulders, covered in dirt and trees that tumbles from thier sides etc.
Think of it as one of those CGI animations where a crude man shape is made from everyday items, but make the shape imitated a dragon and form it from geography.
I'm certain however that lots of Gloranthas do vary on this one.
Ian Cooper