Billingsellida

An order of brachiopods containing the families:
 * Suborder Billingsellidina
 * Superfamily Billingselloidea
 * Family Billingsellidae
 * Suborder Clitambonitidina
 * Superfamily Clitambonitoidea
 * Family Clitambonitidae
 * Family Gonambonitidae
 * Superfamily Polytoechioidea
 * Family Polytoechiidae