Trilobites from the Middle Ordovician Stairway Sandstone, Amadeus Basin, central Australia

Abstract

During the Middle Ordovician (Darriwilian) sandstones and siltstones were deposited in the epicontinental Larapintine Sea, which covered large parts of central Australia. The Darriwilian Stairway Sandstone has, for the first time, been sampled stratigraphically for macrofossils to track marine benthic biodiversity in this clastic-dominated shallow-water palaeoenvironment situated along the margin of northeastern Gondwana. The faunas from the Stairway Sandstone are generally of low diversity and dominated by bivalves but include several animal groups, with trilobites representing 25% of the entire shelly fauna. Thirteen trilobite taxa are described from the Stairway Sandstone; the fauna displays a high degree of endemism. One new species, Basilicus (Parabasilicus) brumbyensis sp. nov. is described.

在中奥陶世 (Darriwilian) 期间, 砂岩和粉砂岩沉积于覆盖着澳大利亚中部大部分地区的陆表海Larapintine Sea。为了研究位于冈瓦纳大陆东北部边缘 的以碎屑岩为主的浅海古环境中海洋底栖生物的多样性, 我们首次对Darriwilian Stairway砂岩按地层序列进行大化石采样。Stairway砂岩的动物群一般分异性低, 以双壳类为主, 但还包括几种动物群体, 三叶虫占整个贝壳动物的25％。从Stairway砂岩中描述的三叶虫有十三个类群; 该动物群显示高土著性。还描述了一个新种, Basilicus (Parabasilicus) brumbyensis sp. nov.。

Acknowledgements

This research was made possible through an FNU (Det Frie Forskningsråd, Natur og Univers) grant, Co-tutelle HDR (Higher Degree Research) funding at Macquarie University and an ARC Discovery Grant # DP120104251 to Glenn A. Brock. Our thanks to Timothy P. Topper, Jan A. Rasmussen, Jakob W. Hansen and Maria Liljeroth (all University of Copenhagen) for help organizing the field campaign to central Australia and, for the latter three persons, assisting during fieldwork. Christine Edgoose and Maxwell Heckenberg (Northern Territory Geological Survey) are thanked for data on the geology at specific localities and for providing equipment for the field campaign. John R. Laurie (Geoscience Australia, Canberra) provided access to specimens in the collections of Geoscience Australia and is thanked for sending relevant literature. Dean Oliver Graphics Pty Ltd completed the final drafts of Figs 1 and 2. David Mathieson and Marissa Betts assisted in the acid laboratory at Macquarie University, to extract conodonts from the material and their efforts are greatly appreciated. Svend Stouge (University of Copenhagen) provided preliminary determinations of the conodonts, which has been very valuable. Steen Lennart Jakobsen (University of Copenhagen) helped by instruction how to produce the best possible latex casts from the material. We would also like to thank Dr Ian Percival (Geological Survey of New South Wales, Sydney) and an anonymous reviewer, for their constructive reviews of the original manuscript.