Preservation and assemblage characteristics of some ornate Lower Devonian Ostracoda from the Humevale Siltstone and Woori Yallock Formation, southeastern Australia

Abstract

The Humevale Siltstone (late Silurian to Early Devonian, Gorstian to Pragian) and Woori Yallock Formation (Early Devonian, Emsian) of central Victoria, Australia, contain rich invertebrate fossil faunas including Ostracoda. Eight ostracod taxa are recognized and illustrated herein: Velibeyrichia wooriyallockensis (Chapman), Velibeyrichia (s.l.) australiae (Chapman), Velibeyrichia sp. 1, Velibeyrichia sp. 2, Beyrichia? ligatura (Chapman), Ulrichia sp., Euglyphella sp. and Strepulites sp. The ostracods are preserved in siltstones and mudstones as natural moulds. Ostracod assemblages are mainly shallow marine and likely include moderate- to low-energy biocoenoses, pseudo-biocoenoses (gravity flow accumulations) and thanatocoenoses.

澳大利亚维多利亚中部的 Humevale粉砂岩（晚志留世 - 早泥盆世，Gorstian阶-Pragian阶）和Woori Yallock组（早泥盆世，Emsian阶）含有丰富的无脊椎动物化石动物群，包括介形类。本文鉴定并描述了八个介形类类群：Velibeyrichia wooriyallockensis（Chapman）、Velibeyrichia（s. l.）australiae（Chapman)、Velibeyrichia sp. 1、Velibeyrichia sp. 2、Beyrichia？ ligatura（Chapman）、Ulrichia sp.、Euglyphella sp.和Strepulites sp.。在介形虫以自然模形式保存在粉砂岩和泥岩中。介形类组合主要是浅海分子，可能包括中至低能量的生物群落、假生物群落（重力流堆积）和尸积群。

Key words:

• beyrichoids
• taxonomy
• palaeoecology
• palaeoenvironment
• shallow marine
• Victoria.

Acknowledgements

Many thanks go to Dr David J. Holloway (Museum Victoria) for his guidance, instruction on techniques and critique of this paper. Thanks go to Museum Victoria staff and volunteers, in particular Dr Rolf Schmidt, for his guidance and assistance with registration of specimens, and Fons Vandenberg, for providing advice on the stratigraphy of the study area. We thank John Laurie for his assistance with borrowing specimens from the Australian Museum. TC thanks John Ward, for his instruction on the Scanning Electron Microscope, and Deakin University staff and students, for use of facilities, support, instructions on software programs and discussions. Two reviewers are thanked for their comments on the first draft of the manuscript. Professor David Siveter is thanked for discussion with M.W. concerning sexual dimorphism in beyrichoid ostracods.