Approaches to the evolution of limbless locomotion

Limblessness is a condition common among reptiles, but rare among endotherms. It provides an excellent working surface for evolutionary studies, as organismic diversity provides us with many interrnediate stages. These are hardly the arrested stages on an ongoing process; however, the structural and behavioral diversity they display provide us with models of past evolutionary stages. This essay provides a summary of past and possibly ongoing studies in analyzing this system.