Article: The Eospiriferidae
The impunctate, spire-bearing family Eospiriferidae contains the subfamilies Eospiriferinae and Cyrtiinae. The Eospiriferinae appear in the Upper Llandovery and persist until the Eifelian; whereas the Cyrtiinae appear in the Upper Llandovery and persist with certainty until the close of the Ludlow, but there is a single specimen from beds of Emsian age in Czechoslovakia. The family is characterized by the possession of radial filar ornamentation externally combined with a spiriferoid form. Internally, the brachial valve is characterized by having long crural plates on either side of a linear, unstriated diductor attachment area. The interior of the pedicle valve is relatively generalized.The eospiriferids disappear from the Western Hemisphere at the end of the Gedinnian, but continue on into the Eifelian in part of the Old World. In the Old World, the eospiriferids are absent from the Rhenish facies of the Devonian, as well as the Devonian of South Africa and Antarctica.The genus Plicocyrtia is proposed for laterally plicate cyrtiinids, and the genera Havlicekia, Macropleura, and Nikiforovaena for eospiriferinids with external forms differing substantially from previously described members of the subfamily. The genera Najadospirifer and Pinguispirifer are rejected from the Eospiriferidae on the basis of differing internal structures and external fine ornamentation.The evolution of plicated eospiriferids from unplicated forms is discussed.