Prokopius, a new name for “Hippocystis sculptus” Prokop, 1965, and the status of the genus Hippocystis Bather, 1919 (Echinodermata; Diploporita)


Authors: Paul CRC

Published in: Bulletin of Geosciences, volume 93, issue 3; pages: 337 - 346; Received 28 November 2017; Accepted in revised form 29 June 2018; Online 20 July 2018

Keywords: Diploporita, Hippocystis, Aristocystitidae, Prokopius gen. nov., Ordovician, Sandbian,

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Bather proposed the genus Hippocystis for some Czech diploporites with horseshoe-shaped diplopores first described by Barrande. Bather cited Aristocystites subcylindricus Barrande as the type species and identified a lectotype, but no specimen accepted by Bather as A. subcylindricus preserved the oral area. Bather believed Aristocystites had irregular haplopores and Hippocystis horseshoe-shaped diplopores without intermediates. In 1965 Prokop redescribed one of Barrande’s original specimens of ?A. subcylindricus as Hippocystis sculptus (Barrande). Its oral area has four ambulacral facets, whereas Aristocystites is unique among the Aristocystitidae in having only two. A complete specimen of A. subcylindricus with the oral area preserved shows only two ambulacral facets. Thus, the type species of Hippocystis belongs to Aristocystites, of which Hippocystis becomes a junior synonym. This leaves ’Hippocystissculptus without a valid generic name. The new name Prokopius is proposed for it. Parsley has shown that horseshoeshaped diplopores also occur in A. bohemicus, type species of Aristocystites. Functional analysis of horseshoe-shaped diplopores suggests they are likely to have evolved repeatedly and so make a poor generic criterion. Characteristic oral areas are much more reliable. Prokopius is distinguished by having an oval mouth, surrounded by eight plates, as in all other aristocystitids, with four vertical ambulacral facets, a zigzag hydropore aligned parallel to the oro-anal line and all these features on a raised oral prominence.


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