Abstract

The holotype of Favosites cylindrica Michelin 1847 is a fragment of corallum completely silicified and poorly preserved.Some specimens, regarded as topotypic (Falls of the Ohio), allow a detailed study of internal characters, wall, pores, and tabulae. Development of horizontal ridges results from folding of the wall. The abundance of these ridges is generally associated with the final stage of growth of the corallum. In ultra-thin sections with polished faces (LFP thin sections), parts of the skeleton not affected by silicification show the microstructural features of the wall. The median "dark line" is composed of granules, sometimes elongated; the stereozone is made of lamellae approximately parallel to the intramural coenozone.A biometric study of the so-called "topotypic" specimens and of the holotype of F. cylindrica shows the conspecificity of all this material.A new genus, Ohiopora, is proposed for F. cylindrica. The new genus is very close to Michelinia sensu stricto, from which it probably was derived but from which it may be distinguished by the presence of horizontal ridges, which form an original feature within the Tabulata.Several old species may be assigned to the new genus, and probably all are synonymous with O. cylindrica.Occurrence: Emsian?, lower and "middle" Eifelian. Ohiopora is endemic of eastern North American province.

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