Trilobites from the mid-Darriwilian (Middle Ordovician) of the Amadeus Basin, central Australia

Abstract

Sixteen species of trilobites are described from the Middle Ordovician (mid-Darriwilian, Da2) Stairway Sandstone and Stokes Siltstone at multiple spot localities from the Amadeus Basin, Northern Territory, central Australia. New trilobite taxa described include two new genera: Ghanaspis gen. nov. and Iridis gen. nov.; as well as five new species; Eisarkaspis jonesi sp. nov., Ghanaspis ritchiei gen. et sp. nov., Iridis schoonorum gen. et sp. nov., Lycophron titan sp. nov., and Norasaphus (Norasaphus) patersoni sp. nov. Of these, Lycophron titan sp. nov. is the largest species of trilobite so far documented from Australia and possibly the third largest in the world. Also redescribed is Basilicus thorntoni [=Asaphus (Megalaspis?) thorntoni] based on the recently rediscovered type material and additional specimens from elsewhere in the basin. *P.M. Smith [Patrick.Smith@austmus.gov.au], Palaeontology Department, Australian Museum Research Institute, Sydney, New South Wales, 2010, Australia and, Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia; J.R. Laurie [john.r.laurie@gmail.com], Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia.