Generic identities and relationships within the brachiopod family Sowerbyellidae

Sowerbyellid brachiopods often formed the dominant constituent in various Late Ordovician and Early Silurian benthic assemblages and had a global distribution under a wide range of water depths on the continental shelves. They persisted after then, but much less abundantly, into the Middle Devonian (Eifelian). However, their classification has varied. The terminology used for each of the individual morphological characters is reviewed and standardised, and those characters are discussed in turn as to their suitability for generic discrimination. Some structures previously used, such as canals developed within the ventral valve hinge area, are now found to be developed polyphyletically within both Sowerbyella and Eochonetes. The systematics of all the nominal genera are reviewed, and synonymies are suggested. Zhilgyzambonites is transferred from the Sowerbyellidae to the Hesperomenidae. Brief revised diagnoses are presented for all the genera and subgenera. Because it is enigmatic, the rare genus Dubioleptina from the Wenlock of Bohemia is revised in detail with new photographs and fresh descriptions, as is the more common but comparably controversial Kozlowskites from the Late Ordovician (Katian) of Bohemia and Wales. Both are confirmed as independent genera.