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New Data on Oikozetetes (Mollusca, Halkieriidae) from the Lower Cambrian of South Australia

Published online by Cambridge University Press:  15 October 2015

Sarah M. Jacquet
Affiliation:
Department of Biological Sciences, Macquarie University, Sydney NSW 2109 Australia ;
Glenn A. Brock
Affiliation:
Department of Biological Sciences, Macquarie University, Sydney NSW 2109 Australia ;
John R. Paterson
Affiliation:
Division of Earth Sciences, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia,

Abstract

A new species of Oikozetetes, O. mounti n. sp. is described from the upper Mernmerna Formation (equivalent to Cambrian Series 2) in the eastern Flinders Ranges, South Australia. Description of both shell morphotypes (morph A and B) from the same stratigraphic horizon favors the interpretation of a two-shelled scleritome for Oikozetetes. Identification of at least two types of halkieriid sclerite (palmates and siculates) in stratigraphic association with the Halkieria-like shells of Oikozetetes suggests that these elements are derived from the same scleritome. This provides evidence against previous suggestions that the Gondwanan species was aspiculate; the scleritome arrangement is interpreted to be similar to Halkieria evangelista Conway Morris and Peel, 1995 and supports placement in the family Halkieriidae Poulsen, 1967. Comparison of modes of accretionary growth in Oikozetetes shell morphotypes to Halkieria shells and terminal plates in modern polyplacophorans, supports a scleritome model that places shell morphs A and B in posterior and anterior locations, respectively, along the axis of the body.

Type
Research Article
Copyright
Copyright © The Paleontological Society 

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