Though not particularly diverse or abundant relative to strophomenides (Strophomenida) or productides (Productida), orthotetides were nevertheless the longest-lasting order of strophomenates, surviving from the Middle Ordovician (“Llanvirn”) up until the Late Permian.

Most fundamental differences between the two orders are internal: orthotetides have more elaborate cardinal processes and a greater diversity of shell microstructure.

Others develop tiny tubercles derived from stacked deflections oriented externally (the extropunctate condition) or internally (pseudopunctate).

The pseudopunctate condition is characteristic of their relatives the strophomenides, with one major difference: orthotetide pseudopunctae always lack taleolae (internal calcite supporting rods).

Despite their similarities, the laminar microstructure of orthotetide and strophomenide shells is most likely a case of convergent evolution, with both groups originating independently from non-laminar brachiopods.

Other trends in orthotetidine evolution include the deepening of the ventral valve, the elongation of the cardinal processes, and the development of a perideltidium (a raised surface adjacent to the pseudodeltidium).