Abstract
A stem-group brachiopod, Oymurania gravestocki Ushatinskaya gen. et sp. nov. is described herein from the middle Atdabanian—lower Botoman Stages (∼Cambrian Stage 3) of the Siberian Platform. The fossils were extracted from limestone beds of the Emyaksin, Perekhod, and Pestrotsvet formations as assemblages of disarticulated orthoconic to cyrtoconic porous shells in apatite preservation. The originally organophosphatic shells of Oymurania are externally similar to mitral sclerites (ventral valves) of the stem-group brachiopod Micrina, although no sellate-like sclerites, nor differentiated subapical area with apophyses were recognised in our material. The range of Oymurania shells with subcentral to posteromarginal apex is similar to that of ventral valves of Mickwitzia. Oymurania is also characterised by the system of radial and orthogonal canals open in pairs or triplets in small depressions or indentations of growth lamellae in the outer shell surface. The orthogonal (Micrina—Setatella type) and radial (h...
Highlights
The originally organophosphatic shells of Oymurania are externally similar to mitral sclerites of the stem-group brachiopod Micrina, no sellate-like sclerites, nor differentiated subapical area with apophyses were recognised in our material
Oymurania is characterised by the system of radial and orthogonal canals open in pairs or triplets in small depressions or indentations of growth lamellae in the outer shell surface
The orthogonal (Micrina–Setatella type) and radial canals are widespread among the early Cambrian stem-group brachiopods, such as Micrina, Mickwitzia, and Setatella
Summary
A stem-group brachiopod, Oymurania gravestocki Ushatinskaya gen. Is described from the middle Atdabanian–lower Botoman Stages (~Cambrian Stage 3) of the Siberian Platform. The fossils were extracted from limestone beds of the Emyaksin, Perekhod, and Pestrotsvet formations as assemblages of disarticulated orthoconic to cyrtoconic porous shells in apatite preservation.
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