Late Silurian pentameride brachiopods from Yass and Molong, New South Wales

Abstract

The five known species of pentameride brachiopods from the Yass Syncline Ludlow (LateSilurian) succession, belonging to the superfamilies Pentameroidea, Gypiduloidea and Clorindoidea, are fully revised; no new species are recognised. The pentameroids Conchidium sp. cf. hospes and Aliconchidium yassi are confined to the Bowspring Limestone Member (Silverdale Formation). The gypiduloid Ascanigypa glabra and externally homeomorphic clorindoids Barrandina wilkinsoni and Clorinda minor replace them in the overlying Barrandella Shale Member, the last two extending into the Yarwood Siltstone Member (Black Bog Shale). Clorinda minor is also possibly present in the Rainbow Hill Member (Rosebank Shale). All except C. minor are uncommon to rare components of the Yass brachiopod fauna. Clorinda molongensis, a species of uncertain mid- to late Silurian age from the Molong Limestone, is also revised. Aliconchidium and Barrandina are known only from Yass, whereas Clorinda is cosmopolitan. Conchidium alsois widespread, but C. hospes is a species from the Prague Basin probably also known from the Urals and the Tien Shan. Ascanigypa is another Prague Basin taxon, recently recognised in Arctic Canada.