The most influential hypothesis in the last 50 years concerning the evolution of polychaete buccal organs is that of Dales (1962).Dales recognised the several basic kinds of buccal organ that will form the basis of this review. They are the simple ventral buccal organ, the muscular ventral buccal organ, the simple axial proboscis and the muscular axial proboscis. However, as can be seen in his summary diagram, he was unable to develop a comprehensive scenario as to the evolutionary transformation among the various kinds of buccal organs.

In their cladistic analysis of relationships among polychaetes Rouse and Fauchald used the work of Dales (1962) and combined his data with subsequent studies and other observations on polychaete anatomy. Their results concerning the evolution of polychaete bucal organs gave difereing results depending on the method used. However one scenario will be used here as the basis for comparison.

Before reviewing the various kinds of buccal organs found in polychaetes we will first summarise the various ways that polychaetes actually feed.