Article: A revision of the brachiopod family Leptocoeliidae

The Leptocoeliidae are redefined to include atrypaceans bearing unbranched plications commonly with a relatively angular cross-section. The common Silurian species Eocoelia hemisphaerica differs from the Devonian members of the Leptocoeliidae in not having a cardinal process. True Leptocoelia occurs in the Precordillera of San Juan and Mendoza, Argentina, this being the first occurrence of the genus in the Malvino-caffric Province of South America and South Africa where Australocoelia (the 'Leptocoelia flabellites1 of most papers on the Lower Devonian of this region) is the common leptocoeliid. Leptocoelia infrequens (Walcott 1884) from the Nevada limestone is redescribed. The new species L. nunezi from the Lower Devonian of Argentina, L. nunezi texana from the Lower Devonian of central Texas and Venezuela, and E. quebecensis from the Lower Silurian of Quebec are described. The leptocoeliids display a progressive tendency toward the loss of the dental lamellae in the pedicle valve during the Lower Silurian (Llandovery), followed by the development of complex cardinal processes in the Lower Devonian. Leptocoeliids have not yet been recognized from the Ludlow. The leptocoeliids are known chiefly from the New World during the Lower and Middle Devonian with the exception of Australocoelia, which also occurs in South Africa and Tasmania, and of Leptocoelia, which also occurs in Kazakhstan.