Latest Cambrian–earliest Ordovician conodonts from far western New South Wales and their biostratigraphical significance

This report documents the conodonts recovered from the Andersons Tank Limestone Member (new name) and calcareous siltstone lenses within the Scropes Range Formation and from the Kandie Tank Limestone within the Kayrunnera Group of the central-southern Koonenberry Belt in far western New South Wales, Australia. Among 18 identifiable conodont species are two new species, <i>Paltodus simplex</i> sp. nov. and <i>Variabiloconus delicatus</i> sp. nov. The conodonts confirm that the age of the Kandie Tank Limestone extends from the latest Cambrian (<i>Cordylodus proavus</i> Biozone) to Early Ordovician (<i>Chosonodina herfurthi</i> Biozone), partly contemporaneous with the Andersons Tank Limestone Member that ranges from the latest Cambrian <i>Cordylodus proavus</i> Biozone to possibly earliest Ordovician (<i>Cordylodus lindstromi</i> Biozone). Occurrence of the index species <i>Iapetognathus fluctivagus</i> and <i>Iapetonudus ibexensis</i> in the middle part of the Kandie Tank Limestone provides direct correlation to the base of the Ordovician System defined at the Green Point section in western Newfoundland of North America, and to sections in Asia and South America. These new data have significantly improved our current understanding of the Ordovician biostratigraphy in the region and more broadly the geological history and evolution of the eastern Gondwana margin during the early Paleozoic. We provide detailed morphological comparison and formal designation of the lectotypes for the four species (<i>I. fluctivagus</i>, <i>Iapetognathus jilinensis</i>, <i>Iapetognathus landingi</i> and <i>I. ibexensis</i>) critical for defining and globally correlating the basal Ordovician. <i>Zhen Y.Y.* [[e-mail]] and I.G. Percival [[e-mail]], Geological Survey of New South Wales, W.B. Clarke Geoscience Center, 947–953 Londonderry Road, Londonderry New South Wales 2753, Australia; P.M. Smith [[e-mail]], Paleontology Department, Australian Museum Research Institute, 1 William Street, Sydney New Sout Wales 2010, Australia, and School of Natural Sciences, 18 Wally’s Walk, Ground Floor, Macquarie University, Sydney New South Wales 2109, Australia; B.D. Webby [[e-mail]], School of Geosciences, University of Sydney, New South Wales 2006, Australia.</i>