A ventral eversible sac-like or lobulated, poorly muscularized buccal organ is present in many polychaetes taxa and maybe the primitive condition for the group.

Scolecida

In this possibly primitive clade of polychaetes a simple ventral buccal organ is found in Orbiniidae, Paraonidae and Questidae, while other members of this clade have a simple axial proboscis.In Orbiniidae, as exemplified here by Leitoscoplos, the outer end of these pharynx may be frilled and densely ciliated and is used for non-selective deposit feeding. In taxa, such as Questidae, the simple ventral buccal organ forms more of a tongue-like structure and is used for 'licking' up sand grains.

Spionida

Members of Spionida all have a pair of grooved feeding palps. The groove is lined with cilia and is generally used to gather food particles. Members of Spionida such as Longosomatidae, Magelonidae, and Poecilochaetidae have a ventral buccal organ that may be used in association with the palps. In this case they are termed to use a form of selective deposit feeding. Other Spionida either lack a buccal organ or have a simple axial proboscis.

Terebellida

Rouse and Fauchald (1997) expanded the traditional membership of Terebellida such that it includes taxa such as Cirratulidae that have a pair of grooved palps like (Spionida) or others such as Terebellidae where may be hundreds of grooved palps. Nevertheless, all members of this redefined Terebellida possess a simple ventral buccal organ, though it is used in different ways. In Terebellidae the multiple grooved palps are used for selective deposit feeding and the ventral buccal organ is involved in sorting the particles when they are brought to the mouth.In Cirratulidae and closely related polychaetes the buccal organ is little different relative to the buccal organ seen in members of Scolecida such Questa.