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 [[email protected]], 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 [[email protected]], Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia.

Keywords:

• Stairway sandstone
• stokes siltstone
• Larapinta Group
• Asaphidae
• Reedocalymeninae
• Northern Territory

Acknowledgements

We are indebted to Alex Ritchie, Robert Jones and others that assisted with fieldwork collections. We also thank Dean Oliver (Dean Oliver Graphics) for the original drafting of Figure 1; Scott Morrison of the University of Oregon for supplying digital versions of the older references which were difficult to obtain; Matthew McCurry of the Australian Museum, Sydney for generously allowing access to the specimens under his care, and kindly allowing PMS to use the camera set-up in the museum’s palaeobiology laboratory. This work was partly supported by funding obtained from the Australian Museum Foundation. Benjamin Kear the editor, Timothy Topper the associate editor and two anonymous reviewers are thanked for their constructive feedback.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was partly supported by funding obtained from the Australian Museum Foundation.