The analysis of thin-walled structures requires a reduction from three to two dimensions. This may be carried out before or together with discretization using either a plate or shell theory, or directly the three dimensional field equations. Despite the fact that in both cases the continuum is degenerated to a surface structure, the term ``degeneration'' is used only for the latter approach. The simplicity in accommodating arbitrarily large deformation and rotation problems is a favorite advantage to degenerated curved shell elements.