Arendt Yu.A.'s Early Carboniferous Echinoderms of the Moscow Region PDF

By Arendt Yu.A.

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1557/87; well-preserved columnal; town of Tarusa, Ignatova Gora quarry, Expo­ sure 9d, Bed 40; Serpukhovian Stage, Lower Ser­ pukhovian Substage, Steshev Horizon (lower part). D e s c r i p t i o n (Figs. 5m and 5n). The column is very small and pentagonal, with a narrow pentagonal axial canal. The articular facet is composed of two equally wide parts (internal and external), both of which are more or less flat but separated form each other by a sharp, almost vertical bend. The internal part is charac­ terized by a slightly tuberculate surface and located in a deep depression where the columnal is very thin.

The columnals are barrel-shaped. The middle part of their lateral surfaces is crossed by longitudinal poorly-developed accessory elevations; its sides bear short, indistinct transverse ridges, each of which con­ tinues a crenelle to the lateral surface. The first-order columnals bear rare crater-shaped cirrus sockets with narrow cylindrical axial canals at their centers and poorly-defined short and wide crenelles on the margins. Such craters occupy half of the columnal height and are located in the middle of its lateral surface.

Genus Breimerocrinus Arendt, gen. nov. E t y m o l o g y . In honor of A. Breimer, the paleon­ tologist who visited the Balstoidea and Crinoidea local­ ity in the Mitino quarry in 1968. T y p e s p e c i e s . Breimerocrinus laevis Arendt, sp. : Serpukhovian Stage, Lower Serpukhovian Substage, Steshev Horizon; southern side of the Mos­ cow Basin. D e s c r i p t i o n . The columns are very small with narrow axial canals. The articular facet is flat, and the central area is wider than a half of the facet.

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Early Carboniferous Echinoderms of the Moscow Region by Arendt Yu.A.

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