Shelly fauna from the Cambrian (Miaolingian, Guzhangian) Shannon Formation and the SPICE event in the Amadeus Basin, Northern Territory

Abstract

Smith, P.M., Brock, G.A. & Paterson J.R. 20 September 2019. Shelly fauna from the Cambrian (Miaolingian, Guzhangian) Shannon Formation and the SPICE event in the Amadeus Basin, Northern Territory. Alcheringa 44, 1–24. ISSN 0311-5518

A low-diversity assemblage of linguliformean brachiopods, hyoliths, molluscs, bradoriid arthropods and echinoderms (ten taxa in total) is documented from the upper Shannon Formation (Cambrian, Miaolingian, Guzhangian; Mindyallan) in the Ross River Syncline and Todd River Anticline area, NE Amadeus Basin, central Australia. Taxa described include: the linguliformean brachiopods Treptotreta jucunda Henderson & MacKinnon, 1981, Opisthotreta sp., Stittia? sp., an undetermined acrotretid and an undetermined linguloid; the molluscs Kobayashiella? heritagensis Webers, Pojeta & Yochelson, 1992 (a paragastropod), and Apoptopegma joyceae sp. nov. (a rostroconch); the bradoriid Mongolitubulus sp.; Hyolithida gen. et sp. indet.; and isolated echinoderm plates. All fauna (including previously documented trilobites) from the upper Shannon Formation disappear at the beginning of a ∼5‰ positive shift in δ¹³C, identified as the Steptoean Positive Isotopic Carbon Excursion (SPICE). Despite previous links between SPICE and a global extinction, as well as the disappearance of all faunal elements in the uppermost Shannon Formation, certain taxa reported herein range through the event elsewhere in the world. The occurrence of Treptotreta jucunda and Kobayashiella? heritagensis in younger (Furongian) deposits indicates these species survived the SPICE extinction event. This study advocates for more systematic and comprehensive sampling through stratigraphic intervals where the SPICE event occurs, especially for range data of complete faunas (rather than individual taxonomic groups), to facilitate a more complete picture of diversity trends through this important phase.

P.M. Smith* [[email protected]], Palaeontology Department, Australian Museum Research Institute, Sydney, New South Wales, 2010, Australia; G.A. Brock [[email protected]], Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia. J.R. Paterson [[email protected]], Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, New South Wales, 2351, Australia. *Also affiliated with: Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia.

Key words:

• brachiopods
• molluscs
• hyoliths
• echinoderms
• bradoriids
• East Gondwana
• Australia.

Acknowledgements

We are indebted to the owners of Loves Creek Station for access to localities near Ross River Gorge. We also wish to thank Geoscience Australia (GA) for access to the spot locality collections. Thanks also to J. Laurie (GA) for organizing extraction and loan of the spot locality material from GA collections and for fruitful discussions on the stratigraphy of the Amadeus and Georgina basins. Aspects of the fieldwork and sample collection were completed with the assistance of S. Houlahan (Macquarie University, Sydney) and R. Smith (Rouse Hill Anglican College). We are also indebted to D. Oliver (Dean Oliver Graphics) for the original drafting of Figs 1, 2. We are grateful to Chief Editor B. Kear, Associate Editor T. Topper, as well as an anonymous referee and C. Skovsted for their constructive reviews, which greatly improved the quality of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by funding from the Macquarie University Postgraduate Fund (to PMS) and the Australian Research Council (DP120104251 to GAB and JRP).