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Morphology, evolution and stratigraphic distribution in the Middle Ordovician conodont genus Microzarkodina

Published online by Cambridge University Press:  01 March 2008

Anita Löfgren
Affiliation:
Department of Geology, Lund University, Sölvegatan 12, SE-223 62 Lund, SwedenE-mail: [email protected]
Tatiana Tolmacheva
Affiliation:
Russian Geological Research Institute, Sredni 74, St Petersburg 199106, Russia E-mail: [email protected]

Abstract

Microzarkodina is a genus of mainly Middle Ordovician conodonts that has its centre of distribution in Baltoscandia, and much less commonly occurs in southern China, Australia, Argentina and Laurentia. In Baltica a series of species, Microzarkodina russica n. sp., M. flabellum, M. parva, M. bella, M. hagetiana and M. ozarkodella, established themselves successfully. The succession of species ranges from just below the base of the Middle Ordovician (M. russica) to the upper part of the Middle Ordovician (M. ozarkodella). The species are frequently used for biostratigraphical purposes. The largely contemporaneous species Microzarkodina bella and M. hagetiana probably both evolved from M. parva and mostly occurred in separate areas. Microzarkodina ozarkodella probably evolved from M. hagetiana. This present investigation is based on a total of 94,208 elements, collected from 20 sections and one drill-core site in Sweden, one drill-core site and one outcrop in Estonia and two sections in the St Petersburg area in Russia. The Microzarkodina apparatus probably consisted of 15 or 17 elements: four P, two or four M and nine S elements. The S elements include different Sa, Sb1, Sb2, and Sc element types.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 2008

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