The Rhynchonelliformea (as described in the Treatise Part H, revised 1997–2007) is divided into five classes: Obolellata, Kutorginata, Chileata, Strophomenata, and Rhynchonellata.

Tooth shapes typically range from deltidiodont (simple and knob-like) to cyrtomatodont (hooked) or transverse (wider than long).

Internally, the rear part of the dorsal valve is complex, bearing a variety of calcified structures originating near the hinge line.

In more recent species, the brachiophores extend into paired crura (singular: crus), which diverge away from the midline and reinforce the base of the lophophore.

In some rhynchonelliform groups, the crura develop further into brachidia (singular: brachidium), looping or spiraling strands which support the entire length of the lophophore.

Likewise, the shell is opened by two pairs of diductor muscles, a lever-like system broadening from the cardinal processes to the central-rear part of the ventral valve.

Apart from muscles and the body cavity, rhynchonelliforms have a system of radiating canals which provide nutrients to the mantle lobes underlying each valve.

Rhynchonelliformea references the family Rhynchonellidae, though rhynchonellides are no more representative of articulate brachiopods than any other group such as spiriferides or strophomenides.

In the older classification of the Treatise on Invertebrate Paleontology Part H (1965), the Class Articulata was divided into six orders: Orthida, Pentamerida, Rhynchonellida, Spiriferida, Terebratulida, and Strophomenida.

Obolellata and Kutorginata were previously included among the inarticulate brachiopods, but have subsequently been recognized as classes of primitive articulates.

Originally these were included as suborders within the Spiriferida, a group which combined brachiopods with spiral (coiled spring-like) brachidia regardless of the orientation or the length of the hinge line or whether the shell was impunctate or punctate.