ABSTRACT
Changes to the classification of the order Strophomenida in the 1965 Brachiopod Treatise have split the Davidsoniacea, with Davidsonia and related genera now placed in the Atrypida, leaving the rest renamed and elevated as the Orthotetidina. Like Davidsonia, the Thecospiridae and Cadomella have proved to have fibrous shell fabrics and spiralia and are also removed to spire–bearing taxa, leaving no strophomenides after the end of the Permian. At least twelve features are important in the characterisation of the Strophomenida, and their distribution within the order. In the resultant classification the Orthotetidina may stand as a sister group to the more closely related Strophomenidina, Chonetidina, Productidina and Strophalosidina, including aulostegoids, richthofeniioids and lyttonioids. The Gemmellaroiidae has been classed with richthofeniids or orthotetids in the past, but the four genera are now grouped with scacchinellids and lyttoniids within the Strophalosiidina, and one genus is possibly an orthotetidine.
