Abstract

The brachythyrid Spiriferella Tschernyschew and horridonids Bailliena n.gen. and Horridonia Chao are described and value as zonal fossils assessed. In ascending order the horridonid sequence is Bailliena yukonensis n.gen. and sp., Pennsylvanian?; Horridonia bullocki n.sp., upper Wolfcampian and lower Leonardian (Lower Permian); H. granulifera (Toula), upper Leonardian or lower Guadalupian (upper Lower Permian). Spiriferella appears confined to the Permian. S. rajah (Salter) subsp. A and S. ordinaria (Einor) range through Wolfcampian and lower Leonardian strata; S. saranae (de Verneuil) and S. editiareatus (Einor) appear restricted to lower Leonardian; S. keilhavii (Buch) and S. rajah (Salter) subsp. B. occur in upper Leonardian and(or) lower Guadalupian.

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