Middle Cambrian brachiopods from the southern Georgina Basin of central Australia

Middle Cambrian brachiopod faunas, dominated by lingulates (linguloids, acrotheloids and acrotretoids) with a minor paterinate component, are documented from the southern Georgina Basin in the Northern Territory. They derive from two lithostratigraphic units: the Thorntonia Limestone of depositional sequence 1 (Ordian age), and the disconformably overlying Arthur Creek Formation, spanning uppermost sequence 1 and all of depositional sequence 2 (latest Ordian to at least Boomerangian age in terms of the Australian stage scale). Apart from one outcrop locality, all specimens were obtained from limestone and dolostone intersected in core from thirteen drillholes. New species described are Aksarinaia subtilicrusta, ?Chakassilingula undulata, Karathele quadrituberculum, Kostjubella robusta, Neotreta circularis, Picnotreta leptorhachis, Micromitra georginaensis and an unnamed new species of Anabolotreta. Kostjubella djagoran (Kruse 1990) is a new combination. Also documented are Kyrshabaktella mudedirri Kruse 1990, Westonia nyapungensis Kruse 1990, Amictocracens teres Henderson & MacKinnon 1981, Stilpnotreta magna Henderson & MacKinnon 1981 and Treptotreta jucunda Henderson & MacKinnon 1981, all of which have previously been recognised in contemporaneous formations from central and northern Australia, western New South Wales, Victoria and New Zealand. Several other forms referable to Kyrshabaktella, ?Orbithele, ?Linnarssonia, ?Treptotreta, ?Batenevotreta, ?Dictyonina and Micromitra are described without formal species assignment.