The problematic ‘chelicerate’ Melbournopterus crossotus Caster & Kjellesvig-Waering: a case of mistaken identity

Abstract

The type (and only known) specimen of Melbournopterus crossotus Caster & Kjellesvig-Waering, an enigmatic late Silurian fossil that was initially assigned to the eurypterid family Stylonuridae, is critically examined for the first time in 60 years. It is reinterpreted as most likely the dorsal valve of a craniate brachiopod, with prominent paired adductor muscle scars (described originally as ‘lateral eyes’) situated anteromedially, a short hingeline and a spinose anterior margin.

James C. Lamsdell [[email protected]], Department of Geology and Paleontological Institute, University of Kansas, 1475 Jayhawk Boulevard, Lawrence, KS 66045, USA; Ian G. Percival [[email protected]], Geological Survey of New South Wales, W.B. Clarke Geoscience Centre, 947–953 Londonderry Road, Londonderry NSW 2753, Australia; Markus Poschmann [[email protected]], Generaldirektion Kulturelles Erbe RLP, Direktion Landesarchäologie, Referat Erdgeschichte, Große Langgasse 29, D-55116 Mainz, Germany. Received 12.10.2012; revised 13.12.2012; accepted 26.12.2012.

问题“螯肢动物”Melbournopterus crossotus Caster & Kjellesvig-Waering: 错误鉴定之例

六十年来第一次批判性研究了Melbournopterus crossotus Caster & Kjellesvig-Waeringde 的模式标本。这是晚志留世的土著化石,最初被归为广翅鲎科Stylonuridae。在此,它被重新确认为很有可能是颅形腕足动物的腹壳,具有一对位于中前部的显见收缩肌痕(最初被描述为“侧眼”)、短铰线和带刺前缘。

Key words:

• Eurypterida
• Stylonuridae
• Xiphosurida
• Brachiopoda
• Craniata
• late Silurian
• Australia

Acknowledgements

J.C.L. thanks Lars Holmer (Uppsala Universitet) and Curtis Congreve (University of Kansas) for discussion on the specimen and Paul Selden (University of Kansas) for support. M.P. thanks Ulrich Jansen (Frankfurt) and Christian Franke (Wallendorf) for useful discussions on brachiopods. The paper benefitted from reviews by John Pickett (Geological Survey of NSW) and Michal Mergl (University of West Bohemia). I.G.P. publishes with permission of the Executive Director, NSW Trade & Investment. We are grateful to David Holloway (Museum Victoria) for facilitating the loan of the holotype. David Barnes (NSW Trade & Investment) photographed the specimens. This is a contribution to IGCP 591: The Early to Middle Paleozoic Revolution.