Ian G. Percival

Late Ordovician nautiloids from central New South Wales, Australia

Nine nautiloid taxa are described from the Late Ordovician sequences (Caradoc-early Ashgill equivalents) of central New South Wales, and include Trocholites costatus sp. nov., Paradiscoceras dissitum sp. nov., Cliefdenoceras gregarium gen. et sp. nov. and Troedssonella sp. The nautiloid fauna occurs chiefly in shallow-water sediments on offshore highs (Parkes Platform and Molong High near Parkes and Orange) of the main volcanic arc in the Tasmanides. This island arc fauna is dominated by nektonic forms. It lacks definite nekto-benthonic forms presumably because deep waters around the highs acted as a barrier to their migration. All taxa except C. gregarium are relatively long ranging and geographically widespread. The presence of Troedssonella in the Fossil Hill Limestone suggests a Llandeilian to early Caradocian age. The fauna is broadly similar to that of the Siberian Platform, Kazakhstan and China, although most elements are cosmopolitan or nearly so. The contemporaneous Tasmanian nautiloid fauna is s...